EN-304-617_v0.0.5.md

3. Attempt to navigate to extension store or marketplace URLs → Verify that extension APIs are undefined or throw errors
4. Verify that extension store pages are blocked or return error → Test that browser shortcuts and commands for extensions are disabled
5. Attempt to install an extension package file directly (drag-and-drop, file picker) → Verify that no extension-related processes or services are running
6. Verify that all installation attempts are rejected with clear messages → Check that browser help documentation does not reference extension features

**Pass Criteria**: No extension installation UI exists AND all installation attempts fail AND extension APIs are unavailable AND no extension-related processes run

**Fail Criteria**: Extension installation is possible through any method OR extension APIs are accessible OR extension UI elements exist

**Evidence**: Screenshots showing absence of extension UI, installation attempt rejection logs, API availability tests showing undefined extension APIs, process list showing no extension services

**References**:

- Browser Security Architecture: https://www.chromium.org/Home/chromium-security/
- Principle of Least Functionality: https://csrc.nist.gov/glossary/term/least_functionality

### Assessment: EXT-REQ-20 (Extension code loading prevention)

**Reference**: EXT-0-REQ-2 - Browser shall block all attempts to load extension code

**Given**: A conformant browser with EXT-0 capability (no extension support)

**Task**: Verify that the browser actively blocks all attempts to load or execute extension code, preventing attackers from bypassing disabled extension UI through protocol handlers, file associations, or exploiting residual extension subsystem components, ensuring that the absence of extension support is enforced at the code execution level and cannot be circumvented through creative attack vectors.

**Verification**:

1. Attempt to load extension code through various vectors: → Verify that no extension content scripts can be injected into pages
   - Direct file:// URL to extension directory
   - Custom protocol handlers (chrome-extension://, moz-extension://)
   - JavaScript injection attempting to load extension scripts
   - Browser command-line flags attempting to enable extensions
2. Verify that all code loading attempts are blocked at the engine level → Attempt to load background scripts or service workers for extensions
3. Test that extension-related protocol schemes return errors or are undefined → Confirm that all extension code execution paths are disabled
4. Attempt to load extension resources through fetch() or XMLHttpRequest → Test that browser does not maintain extension storage databases
5. Verify that all resource loading is rejected with clear error messages → Verify that extension-related directories do not exist or are inaccessible
6. Test that browser does not parse or validate extension manifest files → Check that no extension code is present in browser installation

**Pass Criteria**: All extension code loading attempts are blocked AND extension protocols are undefined AND no extension scripts can execute AND no extension storage exists

**Fail Criteria**: Extension code can be loaded through any vector OR extension protocols function OR extension scripts execute

**Evidence**: Code loading attempt logs showing blocks, protocol scheme test results, resource loading rejection evidence, file system inspection showing no extension directories

**References**:

- Content Security Policy: https://www.w3.org/TR/CSP/
- Web Security Model: https://www.w3.org/Security/wiki/Same_Origin_Policy

### Assessment: EXT-REQ-21 (Extension subsystem removal)

**Reference**: EXT-0-REQ-3 - Browser build shall not include extension subsystem components

**Given**: A conformant browser with EXT-0 capability built without extension support

**Task**: Verify that the browser build completely excludes extension subsystem components at compile time, reducing binary size, eliminating potential vulnerabilities in unused code, and ensuring that extension support cannot be enabled through configuration changes or exploits, providing defense-in-depth by removing the entire extension attack surface rather than merely disabling it.

**Verification**:

1. Inspect browser binary for extension-related symbols or libraries → Verify that extension API bindings are not present in JavaScript engine
2. Use binary analysis tools to verify absence of extension subsystem code → Test that memory footprint is reduced compared to extension-enabled builds
3. Check that extension-related shared libraries are not included in installation → Check that browser about/version page indicates no extension support
4. Verify that browser configuration files contain no extension-related settings → Verify that security update notes do not include extension-related patches
5. Test that no extension-related resources (images, strings, UI elements) exist → Test that browser update mechanism does not fetch extension components
6. Inspect browser source code or build configuration to confirm conditional compilation → Confirm that build variant name or version indicates no extension support

**Pass Criteria**: Binary contains no extension code AND no extension libraries exist AND memory footprint is reduced AND build clearly indicates no extension support

**Fail Criteria**: Extension code exists in binary OR extension libraries are present OR extension support can be enabled through configuration

**Evidence**: Binary analysis reports, library dependency lists, build configuration excerpts, memory usage comparisons, version information showing build variant

**References**:

- Secure Software Development: https://csrc.nist.gov/projects/ssdf
- Attack Surface Reduction: https://www.microsoft.com/en-us/security/blog/topic/attack-surface-reduction/

### Assessment: EXT-REQ-22 (Official extension store restriction)

**Reference**: EXT-1-REQ-13 - Browser shall only allow installation from official curated store

**Given**: A conformant browser with EXT-1 capability (curated extension store only)

**Task**: Verify that the browser restricts extension installation exclusively to official curated stores, preventing sideloading of unreviewed extensions that could contain malware, spyware, or malicious code, ensuring that all installed extensions have undergone security review and comply with store policies, protecting users from supply chain attacks and compromised extension packages distributed through unofficial channels.

**Verification**:

1. Attempt to install an extension from the official curated store → Test that enterprise policies cannot enable sideloading in EXT-1 mode
2. Verify that installation proceeds normally with appropriate permission prompts → Verify that users are informed why sideloading is disabled
3. Attempt to install extension from unofficial sources: → Test that extension update URLs point to official store
   - Direct .crx/.xpi file installation
   - Drag-and-drop extension package
   - Installation via file:// URL
   - Third-party extension marketplaces
4. Verify that all unofficial installation attempts are blocked with clear error messages → Verify that self-hosted extension updates are rejected
5. Test that developer mode is not available to enable sideloading → Check that browser UI provides clear guidance for installing extensions
6. Verify that command-line flags cannot bypass store restriction → Confirm that all installed extensions show official store provenance

**Pass Criteria**: Only official store installation succeeds AND all sideloading is blocked AND no bypass mechanisms exist AND clear user messaging explains restrictions

**Fail Criteria**: Sideloading is possible through any method OR developer mode enables bypasses OR policy overrides exist OR error messages are unclear

**Evidence**: Official store installation success logs, sideloading attempt rejection screenshots, policy configuration tests, extension management UI showing store attribution

**References**:

- Extension Store Policies: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/AMO/Policy
- Supply Chain Security: https://csrc.nist.gov/projects/supply-chain-risk-management

### Assessment: EXT-REQ-23 (Extension security review requirement)

**Reference**: EXT-1-REQ-14 - Extensions shall undergo security review before store publication

**Given**: A conformant browser with EXT-1 capability and access to official extension store

**Task**: Verify that all extensions available in the official curated store have undergone security review before publication, ensuring that automated and manual security checks have identified and prevented malicious code, policy violations, or security vulnerabilities from reaching end users, providing assurance that installed extensions meet minimum security standards and comply with platform policies.

**Verification**:

1. Review extension store security review policies and procedures → Test that extensions can be reported for security issues post-publication
2. Verify that security review includes: → Verify that reported issues trigger re-review process
   - Automated malware scanning
   - Static code analysis for security issues
   - Permission analysis and justification review
   - Manual code review for suspicious patterns
   - Privacy policy and data handling review
3. Attempt to submit a test extension with known security issues: → Check that extensions with security violations are removed from store
   - Excessive permissions without justification
   - Code obfuscation or minification violations
   - Data exfiltration to third-party servers
   - Suspicious API usage patterns
4. Verify that submission is rejected with specific feedback → Verify that security review timeline is reasonable but not bypassable
5. Test that security review findings are communicated to developers → Test that updates also undergo security review
6. Verify that approved extensions display review status or badges → Confirm that review standards are publicly documented

**Pass Criteria**: All extensions undergo security review AND review includes automated and manual checks AND malicious submissions are rejected AND review standards are documented

**Fail Criteria**: Security review can be bypassed OR review is insufficient OR malicious extensions are published OR standards are not disclosed

**Evidence**: Store policy documentation, test submission rejection reports, security review process descriptions, malicious extension removal examples, review timeline data

**References**:

- Extension Review Guidelines: https://extensionworkshop.com/documentation/publish/add-on-policies/
- Secure Development Lifecycle: https://www.microsoft.com/en-us/securityengineering/sdl/

### Assessment: EXT-REQ-24 (Developer mode activation security)

**Reference**: EXT-2-REQ-6 - Developer mode shall require explicit user activation with security warnings

**Given**: A conformant browser with EXT-2 capability (curated store with developer mode)

**Task**: Verify that developer mode requires explicit, informed user activation with clear security warnings, preventing malicious actors from tricking users into enabling developer mode through social engineering, ensuring that users understand the security implications of allowing unreviewed extension code, and providing appropriate warnings about the increased risk of installing extensions that have not undergone official security review.

**Verification**:

1. Attempt to enable developer mode through browser settings → Verify that enterprise policies can prevent developer mode activation
2. Verify that developer mode is disabled by default → Test that re-enabling after disabling shows warning again
3. Verify that enabling developer mode requires multiple deliberate steps: → Verify that developer mode status is clearly indicated in browser UI
   - Navigating to advanced settings section
   - Clicking explicit "Enable Developer Mode" toggle or button
   - Acknowledging security warning dialog
4. Test that security warning explains risks clearly: → Test that users can easily disable developer mode
   - Extensions in developer mode are not reviewed
   - Potential for malicious code execution
   - Risk of data theft or browser compromise
   - Recommendation to only use for development purposes
5. Verify that warning requires affirmative user action (not auto-dismiss) → Verify that disabling developer mode offers to remove developer extensions
6. Test that developer mode cannot be enabled via command-line flags without user consent → Check that developer mode state persists across browser restarts with clear indicators

**Pass Criteria**: Developer mode is disabled by default AND requires explicit multi-step activation AND shows clear security warnings AND enterprise policies can restrict activation

**Fail Criteria**: Developer mode is easy to enable accidentally OR warnings are unclear OR can be bypassed OR no policy controls exist

**Evidence**: Developer mode activation flow screenshots, security warning dialog content, policy configuration tests, UI state indicators

**References**:

- User Security Awareness: https://cheatsheetseries.owasp.org/cheatsheets/User_Privacy_Protection_Cheat_Sheet.html
- Security Warning Design: https://www.usenix.org/conference/soups2020/presentation/reeder

### Assessment: EXT-REQ-25 (Developer mode visual indicators)

**Reference**: EXT-2-REQ-7 - Developer mode extensions shall display persistent visual indicators

**Given**: A conformant browser with EXT-2 capability with developer mode enabled

**Task**: Verify that extensions loaded in developer mode display persistent, prominent visual indicators to continuously remind users that unreviewed code is running in their browser, enabling users to distinguish between vetted store extensions and potentially risky developer extensions, and providing visual cues that can help users identify when developer mode may have been enabled without their knowledge or when they should reconsider the security of their browser configuration.

**Verification**:

1. Enable developer mode and install test developer extension → Test that indicators cannot be hidden or disabled by extensions
2. Verify that developer extension displays visual indicator in extension management UI: → Verify that hovering over indicators explains developer mode risks
   - Special icon, badge, or label
   - Different color or styling
   - Explicit "Developer Mode" or "Unreviewed" text
3. Test that browser toolbar shows indicator when developer extensions are active → Test that new tab pages or security dashboards show developer extension warnings
4. Verify that extension icons have visual badges or overlays → Verify that indicators are visually distinct and noticeable
5. Test that browser status area shows developer mode indicator → Test that multiple developer extensions show cumulative warning
6. Verify that indicators persist across browser restarts → Confirm that disabling developer mode removes all indicators

**Pass Criteria**: Developer extensions have persistent visual indicators AND indicators appear in multiple locations AND indicators cannot be hidden AND indicators explain risks on interaction

**Fail Criteria**: No visual indicators exist OR indicators can be hidden OR indicators are too subtle OR no risk explanation available

**Evidence**: Screenshots of developer extension indicators in various UI locations, persistence test results, user visibility testing, indicator interaction demonstrations

**References**:

- Security Indicators Research: https://www.usenix.org/conference/soups2016/technical-sessions/presentation/felt
- Visual Security Warnings: https://dl.acm.org/doi/10.1145/3290605.3300516

### Assessment: EXT-REQ-26 (Developer mode update disablement)

**Reference**: EXT-2-REQ-8 - Developer mode shall disable automatic extension updates

**Given**: A conformant browser with EXT-2 capability with developer mode enabled

**Task**: Verify that developer mode disables automatic extension updates to prevent developer extensions from silently updating to malicious code without user awareness, ensuring that developers have explicit control over extension versions during development and testing, and preventing attack scenarios where initial benign developer extension updates are replaced with malicious payloads through compromised update mechanisms or developer account takeovers.

**Verification**:

1. Install a developer mode extension with update_url in manifest → Verify that manual update option is available in UI
2. Verify that automatic updates are disabled for the developer extension → Test that manual updates require explicit user action
3. Test that browser does not check for updates automatically: → Verify that update disablement persists across browser restarts
   - Monitor network traffic for update check requests
   - Wait for normal update interval to pass
   - Verify no update checks occur
4. Publish a new version of the extension to the update URL → Test that store-installed extensions continue to receive automatic updates
5. Verify that the extension does not auto-update to new version → Verify that re-installing as store extension re-enables automatic updates
6. Test that extension management UI indicates updates are disabled → Check that extension update policy documentation explains developer mode behavior

**Pass Criteria**: Developer extensions do not auto-update AND no automatic update checks occur AND manual update option exists AND store extensions still update automatically

**Fail Criteria**: Developer extensions auto-update OR update checks occur automatically OR no manual update option OR store extensions lose updates

**Evidence**: Network traffic logs showing no update checks, extension version persistence tests, UI screenshots showing disabled auto-update, manual update flow demonstrations

**References**:

- Extension Update Security: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Updates
- Software Update Best Practices: https://csrc.nist.gov/publications/detail/sp/800-40/rev-4/final

### Assessment: EXT-REQ-27 (Developer mode activity logging)

**Reference**: EXT-2-REQ-9 - Browser shall log all developer mode extension activities

**Given**: A conformant browser with EXT-2 capability with developer mode enabled

**Task**: Verify that the browser comprehensively logs all developer mode extension activities to provide visibility into potentially risky operations performed by unreviewed extensions, enabling security monitoring, incident investigation, and detection of malicious behavior, ensuring that security teams and advanced users can review what developer extensions are doing and identify suspicious patterns that may indicate compromise or abuse.

**Verification**:

1. Enable developer mode and install test developer extension → Test that log retention is appropriate for security analysis
2. Access browser logging interface (console, diagnostic logs, or audit logs) → Verify that logs can be exported or forwarded to monitoring systems
3. Trigger various developer extension activities: → Confirm that logging does not expose sensitive user data
   - Extension installation and loading
   - Permission requests and grants
   - API calls to sensitive interfaces
   - Network requests to external servers
   - Storage access and modifications
   - Content script injections
   - Background script execution
4. Verify that all activities are logged with sufficient detail: → Test that log volume is manageable and does not degrade performance
   - Timestamp of activity
   - Extension ID and name
   - Activity type and description
   - Resources or permissions accessed
   - Success or failure status
5. Test that logs include security-relevant events specifically → Verify that logs distinguish between developer and store extensions
6. Verify that logs are accessible to users and administrators → Check that critical security events trigger additional logging detail

**Pass Criteria**: All developer extension activities are logged AND logs contain sufficient detail for security analysis AND logs are accessible AND logging preserves user privacy

**Fail Criteria**: Activities are not logged OR log detail is insufficient OR logs are inaccessible OR logging exposes sensitive data

**Evidence**: Log excerpts showing various extension activities, log format and field documentation, export functionality demonstrations, privacy analysis of log content

**References**:

- CWE-778: Insufficient Logging: https://cwe.mitre.org/data/definitions/778.html
- OWASP Logging Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Logging_Cheat_Sheet.html

### Assessment: EXT-REQ-28 (Enterprise developer mode control)

**Reference**: EXT-2-REQ-10 - Enterprise policies shall be able to disable developer mode

**Given**: A conformant browser with EXT-2 capability in an enterprise environment

**Task**: Verify that enterprise administrators can completely disable developer mode through policy controls, preventing users from installing unreviewed extensions that could bypass corporate security controls, exfiltrate sensitive data, or compromise compliance requirements, ensuring that organizations can enforce extension security policies appropriate to their risk tolerance and regulatory obligations while still allowing use of approved store extensions.

**Verification**:

1. Access enterprise policy management interface or configuration system → Verify that all attempts to enable developer mode are blocked
2. Identify policy settings related to developer mode (e.g., DeveloperModeDisabled, ExtensionInstallSources) → Test that error messages clearly indicate policy restriction
3. Configure policy to disable developer mode → Verify that users cannot install developer extensions while policy is active
4. Deploy policy through enterprise management tools → Test that previously installed developer extensions are disabled or removed
5. Verify that developer mode toggle is hidden or disabled in browser UI → Verify that policy enforcement persists across browser restarts
6. Attempt to enable developer mode through all available methods: → Test that policy cannot be overridden by local user settings
   - Browser settings UI
   - Command-line flags
   - Configuration file modifications
   - Registry entries (Windows) or preference files

**Pass Criteria**: Enterprise policy can disable developer mode AND all bypass attempts fail AND policy enforcement is persistent AND users receive clear error messages

**Fail Criteria**: Developer mode can be enabled despite policy OR policy can be bypassed OR enforcement is inconsistent OR error messages are unclear

**Evidence**: Policy configuration screenshots, developer mode block demonstrations, policy status verification, audit log entries showing enforcement

**References**:

- Enterprise Browser Management: https://chromeenterprise.google/policies/
- Group Policy Configuration: https://docs.microsoft.com/en-us/deployedge/configure-microsoft-edge

### Assessment: EXT-REQ-29 (Sideloaded extension warnings)

**Reference**: EXT-3-REQ-9 - Sideloaded extensions shall display prominent security warnings

**Given**: A conformant browser with EXT-3 capability (unrestricted extension installation)

**Task**: Verify that sideloaded extensions (installed outside official stores) display prominent, persistent security warnings to inform users of increased risk, ensuring users understand that sideloaded extensions have not undergone official security review, may contain malicious code, and could compromise their privacy or security, enabling informed decisions about whether to continue using extensions from untrusted sources.

**Verification**:

1. Install a test extension via sideloading (direct file installation, not from store) → Test that warnings cannot be permanently dismissed or hidden
2. Verify that installation displays prominent security warning: → Verify that each browser session shows security status
   - Warning about unreviewed extension source
   - Explanation of potential security risks
   - Recommendation to only install trusted extensions
   - Option to cancel installation
3. Test that warning requires affirmative user acknowledgment → Test that extension permissions page emphasizes sideloaded status
4. Verify that installed sideloaded extension shows persistent indicators: → Verify that warning messages are clear and explain risks in user-friendly language
   - Visual badge or label in extension list
   - Warning icon on extension toolbar button
   - Status message in extension details
5. Test that browser status area indicates sideloaded extensions are present → Test that multiple sideloaded extensions show cumulative risk indicators
6. Verify that new tab page or security dashboard shows sideloaded extension warnings → Confirm that uninstalling sideloaded extension removes all warnings

**Pass Criteria**: Sideloaded extensions show prominent warnings at install AND persistent indicators remain visible AND warnings explain security risks clearly AND warnings cannot be hidden

**Fail Criteria**: No warnings shown OR warnings are dismissible OR risk explanation is unclear OR indicators are too subtle

**Evidence**: Installation warning screenshots, persistent indicator demonstrations, security dashboard views, warning message content analysis

**References**:

- Security Warning Effectiveness: https://www.usenix.org/conference/soups2013/proceedings/presentation/akhawe
- Extension Security Best Practices: https://extensionworkshop.com/documentation/develop/build-a-secure-extension/

### Assessment: EXT-REQ-30 (User extension permission controls)

**Reference**: EXT-3-REQ-10 - Browser shall provide user controls to review and revoke extension permissions

**Given**: A conformant browser with EXT-3 capability with installed extensions

**Task**: Verify that users have granular controls to review all granted extension permissions and revoke specific permissions without uninstalling extensions, enabling users to adjust extension access rights as their security preferences evolve, reducing over-privileged extensions, and providing a mechanism to contain potentially compromised extensions by limiting their access to sensitive APIs or data while investigating security concerns.

**Verification**:

1. Install test extensions with various permission sets → Verify that revoking permissions takes effect immediately
2. Access extension management interface → Test that extensions handle permission revocation gracefully (no crashes)
3. Verify that each extension displays complete list of granted permissions → Verify that revoked permissions persist across browser restarts
4. Test that permission list is organized and easy to understand: → Test that extensions can request re-grant of revoked permissions with user consent
   - Grouped by category (site access, API permissions, etc.)
   - Clear descriptions of what each permission enables
   - Visual indicators for high-risk permissions
5. Verify that users can revoke individual permissions through UI controls → Verify that permission changes are logged for user review
6. Test permission revocation for various permission types: → Test that revoking critical permissions triggers warning about potential extension breakage
   - Host permissions (site access)
   - API permissions (cookies, webRequest, etc.)
   - Optional permissions previously granted

**Pass Criteria**: All extension permissions are reviewable AND permissions can be individually revoked AND revocation is immediate and persistent AND extensions handle revocation gracefully

**Fail Criteria**: Permissions are not reviewable OR cannot be revoked individually OR revocation causes crashes OR changes do not persist

**Evidence**: Extension permission UI screenshots, permission revocation demonstrations, persistence tests, extension error handling logs, user control workflow recordings

**References**:

- Runtime Permissions: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/permissions
- User Control Principles: https://www.w3.org/TR/design-principles/#user-control

### Assessment: EXT-REQ-31 (Sideloaded extension malware scanning)

**Reference**: EXT-3-REQ-11 - Browser shall scan sideloaded extensions for known malware signatures

**Given**: A conformant browser with EXT-3 capability allowing sideloaded extensions

**Task**: Verify that the browser automatically scans sideloaded extensions for known malware signatures before installation, providing baseline protection against well-known malicious extensions even in unrestricted installation environments, detecting common malware families, cryptominers, data stealers, and other threats that have been previously identified and catalogued, reducing the risk of users inadvertently installing extensions with confirmed malicious behavior.

**Verification**:

1. Obtain or create test extension packages with known malware signatures: → Test that scan results are logged for security review
   - EICAR test file embedded in extension
   - Known malicious extension samples (from malware repositories)
   - Extensions with known cryptominer code
   - Extensions with data exfiltration patterns
2. Attempt to install each malicious test extension via sideloading → Verify that malware definitions are updated regularly
3. Verify that browser performs pre-installation malware scan → Test that scan performance does not significantly delay installation
4. Verify that malicious extensions are blocked before installation with clear warnings: → Verify that users are informed about scan process
   - Specific threat description (malware type detected)
   - Recommendation to not proceed
   - Option to report malicious extension
5. Test that scan covers all extension components: → Test that detected malware can be quarantined or deleted
   - JavaScript files
   - Background scripts and content scripts
   - Embedded libraries
   - WebAssembly modules
6. Verify that clean extensions pass scan and install normally → Confirm that scan cannot be disabled or bypassed by users

**Pass Criteria**: Malware scanning occurs before installation AND known malware is detected and blocked AND scan covers all extension components AND malware definitions are updated regularly

**Fail Criteria**: No malware scanning occurs OR known malware is not detected OR scan can be bypassed OR definitions are outdated

**Evidence**: Malware detection screenshots, scan log files, test results with various malware samples, malware definition update verification, performance impact analysis

**References**:

- Malware Detection in Browser Extensions: https://research.google/pubs/pub43824/
- Extension Security Analysis: https://www.usenix.org/conference/usenixsecurity12/technical-sessions/presentation/carlini

### Assessment: EXT-REQ-32 (Extension security event logging)

**Reference**: EXT-3-REQ-12 - All extension security events shall be logged for review

**Given**: A conformant browser with EXT-3 capability with extensions installed

**Task**: Verify that all extension security events are comprehensively logged to provide complete audit trail for security monitoring, incident response, and forensic analysis, enabling detection of malicious extension behavior, permission abuse, or security policy violations, ensuring that administrators and security teams have visibility into extension activities that could indicate compromise or misuse in environments with unrestricted extension installation.

**Verification**:

1. Install various test extensions (store, sideloaded, developer mode) → Test that logs are retained for appropriate security analysis period
2. Access browser security logging interface → Verify that logs can be exported or forwarded to SIEM systems
3. Trigger various extension security events: → Confirm that logging does not expose user passwords or sensitive personal data
   - Extension installation from different sources
   - Permission requests and grants/denials
   - Sensitive API usage (debugger, management, privacy)
   - Cross-extension communication attempts
   - Native messaging connections
   - WebRequest interception and modification
   - Suspicious network requests to unusual domains
   - Extension update installations
   - Extension crashes or security errors
   - User permission revocations
4. Verify that all events are logged with comprehensive details: → Test that high-severity events trigger immediate alerts or notifications
   - Timestamp with timezone
   - Extension ID, name, and version
   - Event type and severity level
   - User actions or automated triggers
   - Success/failure status
   - Affected resources (URLs, permissions, APIs)
   - Source of extension (store, sideloaded, developer)
5. Test that logs are structured for automated analysis (JSON, CSV, syslog format) → Verify that logs include contextual information for investigation
6. Verify that logs can be filtered by severity, extension, or event type → Test that log tampering is prevented or detected

**Pass Criteria**: All extension security events are logged AND logs contain comprehensive detail AND logs are structured and filterable AND logs can be exported to SIEM AND logging preserves privacy

**Fail Criteria**: Security events are not logged OR logs lack necessary detail OR logs cannot be analyzed OR logs expose sensitive data OR logs can be tampered with

**Evidence**: Log samples showing various event types, log schema documentation, SIEM integration demonstrations, privacy analysis, retention policy verification, alert configuration examples

**References**:

- CWE-778: Insufficient Logging: https://cwe.mitre.org/data/definitions/778.html
- OWASP Logging Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Logging_Cheat_Sheet.html
- Security Information and Event Management: https://csrc.nist.gov/glossary/term/security_information_and_event_management

## 6.3 Cryptographic Security Assessments

This section covers assessment procedures for requirements ENC-REQ-1 through ENC-REQ-21, addressing TLS/SSL configuration, certificate validation, cryptographic API usage, secure random number generation, and encryption key management.

### Assessment: ENC-REQ-1 (TLS 1.3+ support)

**Reference**: ENC-REQ-1 - Browser shall support TLS 1.3 or higher for all network communications

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that the browser supports modern TLS 1.3 protocol to protect network communications from downgrade attacks, reduce latency through improved handshake efficiency, and provide forward secrecy through ephemeral key exchange, ensuring that user traffic benefits from the latest cryptographic protections against eavesdropping and man-in-the-middle attacks.

**Verification**:

1. Configure a test web server to support multiple TLS versions: TLS 1.0, TLS 1.1, TLS 1.2, and TLS 1.3 → Verify that TLS 1.3 cipher suites are properly supported (TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384, TLS_CHACHA20_POLY1305_SHA256)
2. Navigate the browser to each server endpoint and capture the TLS handshake using packet capture tools (Wireshark, tcpdump) → Confirm that browser successfully negotiates TLS 1.3 when server supports it
3. Verify that the browser successfully negotiates TLS 1.3 when available → Verify that TLS 1.3 is preferred over TLS 1.2 when both are available
4. Configure the server to offer only TLS 1.3 and verify successful connection → Check that browser Security panel shows "TLS 1.3" as the protocol version
5. Test TLS 1.3 features: 0-RTT resumption, encrypted SNI (ESNI/ECH), and post-handshake authentication → Validate that packet captures confirm TLS 1.3 handshake structure (single round-trip)
6. Use browser DevTools Security tab to verify TLS version for the connection → Confirm that TLS 1.3-specific features (0-RTT, encrypted extensions) function correctly
7. Test that browser prefers TLS 1.3 over older versions when both are available → Verify that browser supports all mandatory TLS 1.3 cipher suites

**Pass Criteria**: Browser successfully negotiates TLS 1.3 connections AND prefers TLS 1.3 over older versions when available

**Fail Criteria**: Browser cannot establish TLS 1.3 connections OR prefers older TLS versions when TLS 1.3 is available

**Evidence**: Wireshark packet captures showing TLS 1.3 handshake, DevTools Security tab screenshots, server logs showing negotiated protocol version, cipher suite listings

**References**:

- RFC 8446 - TLS 1.3 Specification: https://datatracker.ietf.org/doc/html/rfc8446
- Mozilla SSL Configuration Generator: https://ssl-config.mozilla.org/
- NIST SP 800-52 Rev. 2 - TLS Guidelines: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-52r2.pdf
- Qualys SSL Labs - SSL/TLS Best Practices: https://github.com/ssllabs/research/wiki/SSL-and-TLS-Deployment-Best-Practices
- Chrome Network Security: https://www.chromium.org/Home/chromium-security/education/tls/

### Assessment: ENC-REQ-2 (Certificate validation)

**Reference**: ENC-REQ-2 - Browser shall perform complete certificate chain validation including expiry, revocation, and trust anchor verification

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that the browser performs comprehensive certificate chain validation to prevent man-in-the-middle attacks using expired, self-signed, or fraudulent certificates, ensuring that only connections to servers with valid certificates from trusted certificate authorities are established without warnings, protecting users from impersonation attacks and ensuring transport layer authentication.

**Verification**:

1. Set up test scenarios with various certificate configurations: → Confirm that valid certificates from trusted CAs are accepted without warnings
   - Valid certificate from trusted CA
   - Expired certificate
   - Self-signed certificate
   - Certificate with wrong hostname (CN/SAN mismatch)
   - Certificate with incomplete chain
   - Certificate from untrusted CA
   - Revoked certificate
2. Navigate to each test endpoint and observe browser behavior → Verify that expired certificates trigger security warnings and connection blocks
3. Verify that browser displays appropriate security warnings for invalid certificates → Check that self-signed certificates are rejected with clear error messages
4. Test that users cannot bypass critical certificate errors without explicit acknowledgment → Validate that hostname mismatches are detected and reported
5. Verify certificate chain validation using browser DevTools Security tab → Confirm that incomplete certificate chains are rejected
6. Test extended validation (EV) certificate display → Verify that certificates from untrusted CAs trigger warnings
7. Capture and analyze the certificate validation process → Check that users should explicitly acknowledge risk to bypass warnings
8. Test certificate validation with intermediate CA certificates → Validate that EV certificates display organization name in browser UI

**Pass Criteria**: All invalid certificates are detected and reported with appropriate warnings AND users cannot silently bypass critical errors

**Fail Criteria**: Any invalid certificate is accepted without warning OR users can bypass critical errors without explicit acknowledgment

**Evidence**: Screenshots of certificate warning dialogs, DevTools Security tab showing certificate validation status, error console logs, packet captures showing certificate exchange

**References**:

- RFC 5280 - X.509 Certificate and CRL Profile: https://datatracker.ietf.org/doc/html/rfc5280
- CA/Browser Forum Baseline Requirements: https://cabforum.org/baseline-requirements-documents/
- OWASP Transport Layer Protection Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Transport_Layer_Protection_Cheat_Sheet.html
- Mozilla Root Store Policy: https://www.mozilla.org/en-US/about/governance/policies/security-group/certs/policy/
- Chrome Certificate Transparency Policy: https://github.com/chromium/ct-policy

### Assessment: ENC-REQ-3 (Certificate pinning support)

**Reference**: ENC-REQ-3 - Browser shall support HTTP Public Key Pinning (HPKP) or alternative certificate pinning mechanisms

**Given**: A conformant browser with encryption capability (ENC-2 or higher)

**Task**: Verify that the browser enforces certificate pinning to prevent man-in-the-middle attacks against critical domains by rejecting connections to pinned sites that present certificates from unexpected certificate authorities, even if those CAs are otherwise trusted, ensuring that even with a compromised certificate authority, attackers cannot impersonate pinned origins through fraudulent certificate issuance.

**Verification**:

1. Configure a test server to send Public-Key-Pins or Expect-CT headers → Test static pins for built-in domains (e.g., Google properties)
2. Navigate to the test server and verify that pins are stored by the browser → Confirm that browser correctly stores certificate pins from HTTP headers
3. Attempt to connect with a certificate that violates the pin (different public key) → Verify that connections with mismatched certificates are rejected
4. Verify that the browser rejects the connection due to pin validation failure → Check that pin validation errors display clear security warnings
5. Test pin expiration and max-age directive behavior → Validate that pins expire according to max-age directive
6. Test includeSubDomains directive for pin inheritance → Confirm that includeSubDomains directive applies pins to subdomains
7. Test report-uri directive for pin violation reporting → Verify that pin violations are reported to specified report-uri
8. Examine browser's HPKP/pin storage (chrome://net-internals/#hsts for Chromium) → Check that browser maintains persistent pin storage across sessions

**Pass Criteria**: Browser enforces certificate pins correctly AND rejects connections that violate pin requirements

**Fail Criteria**: Browser ignores certificate pins OR allows connections that violate pin requirements

**Evidence**: Screenshots of pin validation errors, browser internal state showing stored pins, network logs showing rejected connections, pin violation reports

**References**:

- RFC 7469 - HTTP Public Key Pinning (HPKP): https://datatracker.ietf.org/doc/html/rfc7469
- Expect-CT Header: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Expect-CT
- OWASP Certificate Pinning: https://owasp.org/www-community/controls/Certificate_and_Public_Key_Pinning
- Chrome HPKP Guidance: https://www.chromium.org/hsts/

### Assessment: ENC-REQ-4 (HSTS enforcement)

**Reference**: ENC-REQ-4 - Browser shall enforce HTTP Strict Transport Security (HSTS) to prevent protocol downgrade attacks

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that HSTS enforcement prevents protocol downgrade attacks where attackers strip TLS to intercept credentials, ensuring all connections to HSTS-enabled domains use HTTPS even if users or applications attempt insecure HTTP connections. This protection is critical for preventing man-in-the-middle attacks that exploit the initial HTTP connection window before users type "https://" or before redirects to HTTPS occur.

**Verification**:

1. Configure a test server to send Strict-Transport-Security header: `Strict-Transport-Security: max-age=31536000; includeSubDomains; preload` → Attempt to bypass HSTS with user override and verify it's prevented
2. Navigate to https://test.example.com and verify HSTS header is received → Browser receives and processes Strict-Transport-Security header
3. Attempt to navigate to http://test.example.com (non-HTTPS) and verify automatic upgrade to HTTPS → HTTP requests are automatically upgraded to HTTPS for HSTS domains
4. Test that browser stores HSTS policy persistently across sessions → HSTS policy persists across browser sessions
5. Verify includeSubDomains directive applies HSTS to all subdomains → includeSubDomains directive correctly applies to subdomains
6. Test HSTS policy expiration by setting short max-age values → HSTS policies expire according to max-age directive
7. Examine browser's HSTS storage (chrome://net-internals/#hsts) → Preloaded domains enforce HTTPS even on first visit
8. Test HSTS preload list for well-known domains → Users cannot bypass HSTS enforcement

**Pass Criteria**: All HTTP requests to HSTS domains are automatically upgraded to HTTPS AND HSTS policies are enforced persistently

**Fail Criteria**: HTTP requests are not upgraded OR HSTS policies can be bypassed OR policies do not persist

**Evidence**: Network logs showing HTTP to HTTPS upgrades, browser HSTS storage screenshots, packet captures showing only HTTPS connections, console logs

**References**:

- RFC 6797 - HTTP Strict Transport Security (HSTS): https://datatracker.ietf.org/doc/html/rfc6797
- HSTS Preload List: https://hstspreload.org/
- OWASP HSTS Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Strict_Transport_Security_Cheat_Sheet.html
- MDN HSTS Documentation: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
- Chromium HSTS Implementation: https://www.chromium.org/hsts/

### Assessment: ENC-REQ-5 (Mixed content blocking)

**Reference**: ENC-REQ-5 - Browser shall block mixed content (HTTP resources on HTTPS pages) to prevent downgrade attacks

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that mixed content blocking prevents protocol downgrade attacks where attackers inject HTTP resources into HTTPS pages to intercept data or execute malicious scripts. Blocking mixed content maintains the security guarantees of HTTPS by preventing unencrypted channels that could be exploited by network-level attackers to compromise the page's integrity and confidentiality.

**Verification**:

1. Create an HTTPS test page (https://test.example.com) that loads various HTTP resources: → Active mixed content (scripts, stylesheets, iframes) is completely blocked
   - HTTP scripts: `<script src="http://example.com/script.js">`
   - HTTP stylesheets: `<link href="http://example.com/style.css">`
   - HTTP iframes: `<iframe src="http://example.com/page.html">`
   - HTTP images: `<img src="http://example.com/image.jpg">`
   - HTTP XHR/fetch requests
   - HTTP form submission actions
2. Navigate to the test page and observe browser behavior → Browser console displays clear mixed content blocking messages
3. Verify that active mixed content (scripts, stylesheets, iframes) is blocked → Passive mixed content may load with warnings (or be blocked in strict mode)
4. Test browser's handling of passive mixed content (images, audio, video) → Mixed content indicator appears in browser address bar/security indicator
5. Check browser console for mixed content warnings → CSP block-all-mixed-content directive blocks all mixed content
6. Test Content-Security-Policy: block-all-mixed-content directive → CSP upgrade-insecure-requests upgrades HTTP resources to HTTPS
7. Verify that upgrade-insecure-requests CSP directive upgrades HTTP to HTTPS → Form submissions to HTTP URLs are blocked or warned
8. Test mixed content indicator in browser address bar → Users are warned about security implications of mixed content

**Pass Criteria**: All active mixed content is blocked AND clear warnings are displayed in console and UI

**Fail Criteria**: Active mixed content loads successfully OR no warnings are displayed

**Evidence**: Browser console screenshots showing blocked resources, network panel showing blocked requests, security indicator screenshots, DevTools showing CSP violations

**References**:

- W3C Mixed Content Specification: https://w3c.github.io/webappsec-mixed-content/
- MDN Mixed Content Documentation: https://developer.mozilla.org/en-US/docs/Web/Security/Mixed_content
- Chrome Mixed Content Policy: https://blog.chromium.org/2019/10/no-more-mixed-messages-about-https.html
- Upgrade Insecure Requests: https://www.w3.org/TR/upgrade-insecure-requests/

### Assessment: ENC-REQ-6 (Certificate Transparency)

**Reference**: ENC-REQ-6 - Browser shall enforce Certificate Transparency (CT) requirements for all publicly trusted certificates

**Given**: A conformant browser with encryption capability (ENC-2 or higher)

**Task**: Verify that Certificate Transparency enforcement detects rogue certificates issued by compromised or malicious certificate authorities, preventing attackers from using fraudulently issued certificates for man-in-the-middle attacks. CT ensures all publicly trusted certificates are logged in append-only public ledgers, making unauthorized certificate issuance detectable and accountable.

**Verification**:

1. Set up test servers with certificates that have different CT compliance levels: → Browser accepts certificates with valid SCTs
   - Certificate with embedded SCTs (Signed Certificate Timestamps)
   - Certificate with SCTs delivered via TLS extension
   - Certificate with SCTs delivered via OCSP stapling
   - Certificate without any SCTs
2. Navigate to each test server and observe browser behavior → Certificates without SCTs are rejected with security errors
3. Verify that browser requires CT for publicly trusted certificates → DevTools Security tab displays CT compliance status
4. Check DevTools Security tab for CT information → Browser validates SCT signatures from known logs
5. Test that certificates without valid SCTs are rejected → CT is enforced for all publicly trusted certificates
6. Verify that browser validates SCT signatures → Multiple SCT delivery mechanisms are supported
7. Test CT enforcement for different certificate types (DV, OV, EV) → Browser maintains list of trusted CT log servers
8. Examine browser's CT policy compliance → CT violations trigger certificate errors

**Pass Criteria**: Browser enforces CT requirements AND rejects certificates without valid SCTs

**Fail Criteria**: Browser accepts certificates without SCTs OR does not validate SCT signatures

**Evidence**: DevTools Security tab screenshots showing CT status, certificate error dialogs for non-CT certificates, network logs showing SCT validation, browser CT policy configuration

**References**:

- RFC 6962 - Certificate Transparency: https://datatracker.ietf.org/doc/html/rfc6962
- Chrome CT Policy: https://github.com/chromium/ct-policy/blob/master/ct_policy.md
- Certificate Transparency Overview: https://certificate.transparency.dev/
- Google CT Log List: https://www.gstatic.com/ct/log_list/v3/all_logs_list.json
- CT Monitoring: https://developers.google.com/web/updates/2017/10/certificate-transparency

### Assessment: ENC-REQ-7 (OCSP stapling)

**Reference**: ENC-REQ-7 - Browser shall support OCSP stapling for efficient certificate revocation checking

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that OCSP stapling support enables efficient certificate revocation checking without privacy leaks, preventing attackers from using revoked certificates while avoiding OCSP responder queries that reveal user browsing patterns. Stapling moves the revocation check to the server, improving performance and privacy while maintaining security against compromised certificates.

**Verification**:

1. Configure a test server to support OCSP stapling (include OCSP response in TLS handshake) → Verify handling of expired or invalid OCSP responses
2. Navigate to the test server and capture the TLS handshake using packet capture tools → Browser successfully receives and validates stapled OCSP responses
3. Verify that browser receives and validates the stapled OCSP response → Packet captures show OCSP response in TLS handshake (CertificateStatus message)
4. Test server without OCSP stapling and verify browser falls back to OCSP responder query → Browser validates OCSP response signatures
5. Configure OCSP response indicating certificate is revoked and verify browser rejection → Revoked certificates are rejected based on OCSP response
6. Test OCSP response validation including signature verification → Browser falls back to direct OCSP query when stapling unavailable
7. Measure performance difference between stapled and non-stapled OCSP → OCSP Must-Staple extension is enforced (if present)
8. Test OCSP Must-Staple certificate extension enforcement → Performance metrics show faster connection with stapling

**Pass Criteria**: Browser correctly validates stapled OCSP responses AND rejects revoked certificates

**Fail Criteria**: Browser ignores OCSP responses OR accepts revoked certificates

**Evidence**: Packet captures showing stapled OCSP in TLS handshake, certificate error screenshots for revoked certificates, performance measurements, DevTools Security tab showing OCSP status

**References**:

- RFC 6066 - TLS Extension: OCSP Status Request: https://datatracker.ietf.org/doc/html/rfc6066#section-8
- RFC 6960 - Online Certificate Status Protocol (OCSP): https://datatracker.ietf.org/doc/html/rfc6960
- OCSP Stapling Explained: https://www.digicert.com/kb/ssl-support/what-is-ocsp-stapling.htm
- OCSP Must-Staple: https://scotthelme.co.uk/ocsp-must-staple/

### Assessment: ENC-REQ-8 (Cipher suite restrictions)

**Reference**: ENC-REQ-8 - Browser shall support only secure cipher suites and disable weak or deprecated algorithms

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that cipher suite restrictions prevent cryptographic weaknesses from being exploited by attackers to break TLS encryption, ensuring only modern algorithms resistant to known attacks are used. Rejecting weak ciphers like RC4, DES, and export-grade algorithms prevents downgrade attacks and ensures forward security against future cryptanalysis.

**Verification**:

1. Configure test servers with various cipher suites: → Test cipher suite restrictions for different TLS versions
   - Strong: TLS_AES_256_GCM_SHA384, TLS_CHACHA20_POLY1305_SHA256
   - Acceptable: TLS_AES_128_GCM_SHA256, ECDHE-RSA-AES128-GCM-SHA256
   - Weak: RC4, DES, 3DES, NULL ciphers
   - Export-grade ciphers
2. Test browser connection to each server configuration → Browser successfully negotiates strong cipher suites
3. Verify that browser refuses weak cipher suites → Weak cipher suites (RC4, DES, 3DES, NULL) are rejected
4. Capture cipher suite negotiation using packet analysis → Connection fails when only weak ciphers are available
5. Test browser's cipher suite preference order → Browser prefers AEAD ciphers over CBC-mode ciphers
6. Verify that AEAD (Authenticated Encryption with Associated Data) ciphers are preferred → Cipher suite negotiation follows secure ordering
7. Test that CBC-mode ciphers are avoided or deprioritized → Export-grade ciphers are completely disabled
8. Examine browser's supported cipher suite list → DevTools shows negotiated cipher suite

**Pass Criteria**: Browser only accepts strong cipher suites AND rejects all weak or deprecated ciphers

**Fail Criteria**: Browser accepts any weak cipher suite OR fails to negotiate strong ciphers when available

**Evidence**: Packet captures showing cipher suite negotiation, DevTools Security tab showing negotiated cipher, server logs, connection error screenshots for weak cipher servers

**References**:

- Mozilla SSL Configuration Generator: https://ssl-config.mozilla.org/
- NIST SP 800-52 Rev. 2 - TLS Guidelines: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-52r2.pdf
- RFC 8446 - TLS 1.3 Cipher Suites: https://datatracker.ietf.org/doc/html/rfc8446#appendix-B.4
- IANA TLS Cipher Suite Registry: https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-4
- Qualys SSL Labs - Cipher Suite Guidance: https://github.com/ssllabs/research/wiki/SSL-and-TLS-Deployment-Best-Practices#23-use-secure-cipher-suites

### Assessment: ENC-REQ-9 (Perfect forward secrecy)

**Reference**: ENC-REQ-9 - Browser shall support and prefer cipher suites with perfect forward secrecy (PFS)

**Given**: A conformant browser with encryption capability (ENC-2 or higher)

**Task**: Verify that perfect forward secrecy prevents retrospective decryption attacks where adversaries record encrypted traffic and later compromise server private keys to decrypt historical sessions. PFS ensures that even if long-term keys are compromised, past TLS sessions remain secure because session keys were ephemeral and never stored.

**Verification**:

1. Configure test servers with different key exchange mechanisms: → Test connection failure when only non-PFS ciphers are available
   - ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) - provides PFS
   - DHE (Diffie-Hellman Ephemeral) - provides PFS
   - RSA key exchange - no PFS
2. Test browser connection to each server configuration → Browser successfully negotiates ECDHE/DHE cipher suites
3. Verify that browser prefers ECDHE/DHE over static RSA key exchange → Browser prefers PFS cipher suites over non-PFS alternatives
4. Capture TLS handshake to confirm ephemeral key exchange → Packet captures show ephemeral key exchange in handshake
5. Test that browser supports multiple elliptic curves (X25519, P-256, P-384) → Browser supports modern elliptic curves (X25519 preferred)
6. Verify proper DH parameter size enforcement (minimum 2048 bits) → DHE parameters meet minimum security requirements (2048+ bits)
7. Test TLS 1.3 behavior (all cipher suites provide PFS) → TLS 1.3 connections always provide PFS
8. Examine cipher suite preference order for PFS priority → DevTools Security tab indicates PFS status

**Pass Criteria**: Browser prefers PFS cipher suites when available AND successfully negotiates ephemeral key exchange

**Fail Criteria**: Browser prefers non-PFS ciphers over PFS alternatives OR fails to negotiate PFS key exchange

**Evidence**: Packet captures showing ECDHE/DHE key exchange, DevTools Security tab showing PFS cipher suite, connection test results, cipher suite preference analysis

**References**:

- RFC 8446 - TLS 1.3 (all cipher suites provide PFS): https://datatracker.ietf.org/doc/html/rfc8446
- Perfect Forward Secrecy Explained: https://scotthelme.co.uk/perfect-forward-secrecy/
- OWASP TLS Cheat Sheet - Forward Secrecy: https://cheatsheetseries.owasp.org/cheatsheets/Transport_Layer_Protection_Cheat_Sheet.html#forward-secrecy
- Mozilla Server Side TLS Guidelines: https://wiki.mozilla.org/Security/Server_Side_TLS

### Assessment: ENC-REQ-10 (Revocation checking)

**Reference**: ENC-REQ-10 - Browser shall perform certificate revocation checking via OCSP and/or CRL mechanisms

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that certificate revocation checking prevents attackers from using compromised or fraudulently obtained certificates that have been revoked by the issuing CA. Checking revocation status ensures browsers reject certificates known to be untrustworthy, protecting users from man-in-the-middle attacks using stolen or misused certificates even after they've been marked as invalid.

**Verification**:

1. Set up test certificates with different revocation configurations: → Test browser's revocation checking cache behavior
   - Valid certificate with OCSP responder URL
   - Valid certificate with CRL distribution point
   - Revoked certificate (marked as revoked in OCSP/CRL)
   - Certificate without revocation information
2. Navigate to servers using each certificate type → Browser performs OCSP queries for certificates with OCSP URLs
3. Verify that browser checks certificate revocation status → Browser downloads and processes CRLs when available
4. Test OCSP responder queries (use network monitoring) → Revoked certificates are rejected with clear error messages
5. Test CRL download and parsing → Browser caches revocation check results appropriately
6. Configure OCSP responder to return "revoked" status and verify browser rejection → OCSP responses are validated (signature, freshness)
7. Test soft-fail vs hard-fail behavior when revocation check is unavailable → CRL validity period is checked
8. Measure performance impact of revocation checking → Browser handles revocation check failures gracefully

**Pass Criteria**: Browser performs revocation checks AND rejects revoked certificates with clear error messages

**Fail Criteria**: Browser skips revocation checking OR accepts revoked certificates

**Evidence**: Network logs showing OCSP/CRL requests, certificate error screenshots for revoked certificates, packet captures, DevTools showing revocation status, performance measurements

**References**:

- RFC 6960 - Online Certificate Status Protocol (OCSP): https://datatracker.ietf.org/doc/html/rfc6960
- RFC 5280 - Certificate and CRL Profile: https://datatracker.ietf.org/doc/html/rfc5280
- Chrome CRLSet Mechanism: https://www.imperialviolet.org/2012/02/05/crlsets.html
- OWASP Certificate Revocation: https://owasp.org/www-community/controls/Certificate_and_Public_Key_Pinning

### Assessment: ENC-REQ-11 (Web Crypto API compliance)

**Reference**: ENC-REQ-11 - Browser shall implement W3C Web Cryptography API for JavaScript cryptographic operations

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that Web Crypto API compliance provides secure, browser-native cryptographic operations preventing developers from implementing insecure custom cryptography that could be vulnerable to timing attacks, weak random number generation, or algorithmic flaws. Restricting the API to secure contexts ensures cryptographic keys and operations are only available over HTTPS, preventing network attackers from intercepting keys.

**Verification**:

1. Create test web page accessing window.crypto.subtle API → window.crypto.subtle is available in secure contexts only
2. Test key generation for various algorithms: → All mandatory algorithms are supported
   - RSA-OAEP, RSA-PSS (2048, 3072, 4096 bits)
   - ECDSA, ECDH (P-256, P-384, P-521 curves)
   - AES-GCM, AES-CBC (128, 256 bits)
   - HMAC with various hash functions
3. Test encryption/decryption operations with generated keys → Key generation produces keys of requested type and size
4. Test signing and verification operations → Encrypt/decrypt operations work correctly with proper padding
5. Test key derivation functions (PBKDF2, HKDF) → Sign/verify operations validate signatures correctly
6. Test key import/export in various formats (JWK, PKCS8, SPKI, raw) → Key derivation functions produce deterministic results
7. Verify that subtle crypto operations are only available in secure contexts (HTTPS) → Non-extractable keys cannot be exported
8. Test that cryptographic keys can be marked as non-extractable → Key usage constraints are enforced
9. Test key usage constraints (encrypt, decrypt, sign, verify, etc.) → Operations fail appropriately in insecure contexts (HTTP)
10. Verify proper error handling for invalid parameters → Error messages are clear and informative

**Pass Criteria**: All Web Crypto API operations function correctly AND API is restricted to secure contexts

**Fail Criteria**: Required algorithms are missing OR API is available in insecure contexts OR operations produce incorrect results

**Evidence**: Console logs showing successful crypto operations, test result screenshots, code demonstrating API usage, error messages for insecure context access

**References**:

- W3C Web Cryptography API Specification: https://www.w3.org/TR/WebCryptoAPI/
- MDN Web Crypto API Documentation: https://developer.mozilla.org/en-US/docs/Web/API/Web_Crypto_API
- Web Crypto API Examples: https://github.com/diafygi/webcrypto-examples
- OWASP Cryptographic Storage Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Cryptographic_Storage_Cheat_Sheet.html
- Chrome Web Crypto Implementation: https://www.chromium.org/blink/webcrypto/

### Assessment: ENC-REQ-12 (Secure random number generation)

**Reference**: ENC-REQ-12 - Browser shall provide cryptographically secure random number generation via Crypto.getRandomValues()

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that cryptographically secure random number generation prevents predictability attacks where weak randomness allows attackers to guess session tokens, cryptographic keys, or authentication nonces. High-quality entropy ensures generated values are unpredictable and cannot be reproduced, which is essential for secure key generation, token creation, and cryptographic operations.

**Verification**:

1. Create test page calling window.crypto.getRandomValues() with various typed arrays: → window.crypto.getRandomValues() is available and functional
   - Uint8Array, Uint16Array, Uint32Array
   - Different array sizes (1 byte to 65536 bytes)
2. Generate large samples of random data (millions of bytes) → Generated values pass statistical randomness tests
3. Test statistical properties of generated random data: → Repeated calls produce different, unpredictable values
   - Frequency test (chi-square)
   - Runs test
   - Entropy analysis
4. Verify that repeated calls produce different values → All typed array types are supported
5. Test that maximum size limit (65536 bytes) is enforced → Maximum size limit (65536 bytes) is enforced
6. Verify proper error handling for invalid parameters → QuotaExceededError thrown for oversized requests
7. Test that random values are available in both secure and insecure contexts → Random values have sufficient entropy (>= 7.9 bits per byte)
8. Compare randomness quality across multiple browser sessions → Performance is acceptable (can generate MBs per second)
9. Test performance of random number generation → API is available in all contexts (secure and insecure)

**Pass Criteria**: Generated random values pass statistical tests AND have sufficient entropy for cryptographic use

**Fail Criteria**: Random values show statistical bias OR have insufficient entropy OR values are predictable

**Evidence**: Statistical test results, entropy analysis graphs, performance benchmarks, console logs showing API usage, test code with results

**References**:

- W3C Web Cryptography API - getRandomValues: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
- MDN Crypto.getRandomValues(): https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
- NIST SP 800-22 - Statistical Tests for Random Number Generators: https://csrc.nist.gov/publications/detail/sp/800-22/rev-1a/final
- Random.org - Statistical Tests: https://www.random.org/analysis/
- OWASP Cryptographic Storage - Random Number Generation: https://cheatsheetseries.owasp.org/cheatsheets/Cryptographic_Storage_Cheat_Sheet.html#secure-random-number-generation

### Assessment: ENC-REQ-13 (SubResource Integrity)

**Reference**: ENC-REQ-13 - Browser shall enforce Subresource Integrity (SRI) for externally loaded scripts and stylesheets

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that Subresource Integrity enforcement prevents supply chain attacks where compromised CDNs or third-party servers deliver malicious modified scripts or stylesheets. SRI ensures that external resources match their expected cryptographic hashes, detecting unauthorized modifications that could inject malware, steal credentials, or compromise user data even if the hosting server is compromised.

**Verification**:

1. Create test page loading external resources with integrity attributes: → Resources with matching integrity hashes load and execute successfully
   ```html
   <script src="https://cdn.example.com/lib.js"
           integrity="sha384-oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxy9rx7HNQlGYl1kPzQho1wx4JwY8wC"
           crossorigin="anonymous"></script>
   <link href="https://cdn.example.com/style.css"
         integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN"
         crossorigin="anonymous">
   ```
2. Verify that resources with correct integrity hashes load successfully → Resources with mismatched hashes are blocked from loading
3. Modify resource content to mismatch integrity hash and verify blocking → Browser console displays clear SRI violation errors
4. Test multiple hash algorithms: sha256, sha384, sha512 → Multiple hash algorithms (sha256, sha384, sha512) are supported
5. Test multiple integrity values (fallback hashes) → Multiple integrity values allow fallback verification
6. Test CORS requirement for cross-origin SRI resources → Cross-origin resources require proper CORS headers for SRI
7. Verify browser console errors for SRI failures → SRI failures prevent resource execution/application
8. Test SRI with different resource types (scripts, stylesheets, preload links) → Network panel shows blocked resources with SRI violations
9. Test that SRI failures prevent script execution/style application → Page functionality degrades gracefully when SRI blocks resources

**Pass Criteria**: Resources with correct integrity hashes load successfully AND resources with mismatched hashes are blocked with clear errors

**Fail Criteria**: Resources with mismatched hashes load and execute OR no error messages displayed

**Evidence**: Browser console screenshots showing SRI errors, network panel showing blocked resources, test page demonstrating SRI enforcement, DevTools showing integrity attribute validation

**References**:

- W3C Subresource Integrity Specification: https://www.w3.org/TR/SRI/
- MDN Subresource Integrity: https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity
- SRI Hash Generator: https://www.srihash.org/
- OWASP SRI Guidance: https://cheatsheetseries.owasp.org/cheatsheets/Third_Party_Javascript_Management_Cheat_Sheet.html#subresource-integrity
- Chrome SRI Implementation: https://www.chromium.org/Home/chromium-security/education/tls/

### Assessment: ENC-REQ-14 (Encrypted SNI)

**Reference**: ENC-REQ-14 - Browser shall support Encrypted Server Name Indication (ESNI/ECH) to prevent SNI-based censorship and surveillance

**Given**: A conformant browser with encryption capability (ENC-3 or higher)

**Task**: Verify that Encrypted SNI support prevents network surveillance and censorship where adversaries monitor TLS handshakes to identify which websites users visit, enabling targeted blocking or surveillance. Encrypting SNI protects user privacy by hiding the destination hostname from network observers, preventing traffic analysis attacks that reveal browsing patterns even when connections use HTTPS.

**Verification**:

1. Configure a test server supporting Encrypted Client Hello (ECH) or ESNI → Examine browser settings for ECH/ESNI enablement
2. Publish ECH configuration in DNS (TLS HTTPS record type 65) → Browser successfully negotiates ECH/ESNI when available
3. Navigate browser to the test server → SNI extension is not visible in cleartext in packet captures
4. Capture TLS handshake using packet analysis tools → ClientHello contains encrypted_client_hello extension
5. Verify that SNI extension is encrypted in ClientHello message → Browser retrieves ECH configuration via DNS
6. Test fallback behavior when ECH is unavailable → Fallback to cleartext SNI works when ECH unavailable
7. Test that cleartext SNI is not visible in packet captures → DNS queries for ECH config are encrypted (DoH/DoT)
8. Verify browser DNS-over-HTTPS (DoH) or DNS-over-TLS (DoT) usage for ECH config retrieval → Browser DevTools or internal pages show ECH status
9. Test ECH with split-horizon DNS configurations → Connection succeeds with ECH-enabled servers

**Pass Criteria**: Browser encrypts SNI when ECH is available AND cleartext SNI is not visible in packet captures

**Fail Criteria**: SNI is transmitted in cleartext when ECH is available OR browser doesn't support ECH

**Evidence**: Packet captures showing encrypted ClientHello, Wireshark analysis showing absence of cleartext SNI, DNS query logs showing ECH config retrieval, browser configuration screenshots

**References**:

- RFC 8744 - Encrypted Server Name Indication (ESNI): https://datatracker.ietf.org/doc/html/rfc8744
- Encrypted Client Hello (ECH) Draft: https://datatracker.ietf.org/doc/html/draft-ietf-tls-esni
- Cloudflare ECH Announcement: https://blog.cloudflare.com/encrypted-client-hello/
- Mozilla ECH Implementation: https://support.mozilla.org/en-US/kb/understand-encrypted-client-hello
- Chrome ECH Status: https://chromestatus.com/feature/6196703843581952

### Assessment: ENC-REQ-15 (Certificate error UI)

**Reference**: ENC-REQ-15 - Browser shall display clear, prominent warnings for certificate errors with appropriate risk communication

**Given**: A conformant browser with encryption capability (ENC-1 or higher)

**Task**: Verify that certificate error UI effectively warns users about man-in-the-middle attacks or compromised servers before they transmit sensitive data to untrusted connections. Clear, prominent warnings with appropriate risk communication prevent users from inadvertently trusting malicious certificates, while making bypass actions deliberately difficult discourages risky behavior that could expose credentials or personal information.

**Verification**:

1. Create test scenarios for various certificate errors: → Certificate errors trigger full-page interstitial warnings
   - Expired certificate
   - Untrusted CA
   - Hostname mismatch
   - Self-signed certificate
   - Revoked certificate
   - Weak signature algorithm (SHA-1)
   - Invalid certificate chain
2. Navigate to each error scenario and document browser UI response → Warning messages clearly explain the security risk
3. Verify that warning messages clearly communicate security risk → Users should take explicit action to bypass (not easy clickthrough)
4. Test that warnings are difficult to bypass (require explicit user action) → Technical details are accessible via "Advanced" or similar link
5. Evaluate warning message clarity for non-technical users → Certificate details can be viewed and inspected