Network Working Group T. Jahnke Internet-Draft Aviontex GmbH Intended status: Standards Track May 30, 2025 Expires: November 30, 2025 Certificate Authority Self-Revocation Extension draft-jahnke-ca-self-revocation-00 Abstract This document defines a cryptographically secure mechanism for Certificate Authorities (CAs) to perform controlled self-revocation upon compromise detection. The mechanism provides automated detection with mandatory manual authorization, enabling CA operators to terminate CA validity within hours instead of months while maintaining strict dual-person control. This addresses operational gaps in current PKI infrastructure exposed by historical incidents such as DigiNotar (2011) and Symantec certificate misissuance, where extended cleanup periods affected millions of users globally. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on November 30, 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction ....................................................3 2. Conventions Used in This Document ...............................4 3. Terminology .....................................................5 4. Problem Statement ...............................................6 5. Solution Overview ...............................................8 6. Self-Revocation Extension Definition ...........................10 7. Implementation Requirements ....................................15 8. Operational Procedures .........................................18 9. Security Considerations ........................................20 10. IANA Considerations ...........................................25 11. Deployment Considerations .....................................26 12. References ....................................................27 Appendix A. Implementation Examples ...............................29 1. Introduction Current Public Key Infrastructure (PKI) lacks an efficient mechanism for Certificate Authorities (CAs) to rapidly terminate their own validity upon key compromise detection. Historical incidents have demonstrated that CA compromise cleanup can require months or years, during which time attackers can continue to issue fraudulent certificates. This work was developed as part of security enhancements for the keweonDNS project by Aviontex GmbH, a public DNS-Security infrastructure requiring high-security PKI implementation. The critical nature of public DNS infrastructure demands PKI solutions that can respond to compromise incidents within hours rather than months, while maintaining strict operational controls. 1.1. Genesis of This Solution This specification originated from a practical PKI implementation project that exposed fundamental gaps in existing standards. While developing an enterprise PKI system for public DNS-Security infrastructure, the authors encountered the realization that a compromised Root CA has no standardized method for rapid self-termination. The key insight emerged during a discussion of threat scenarios: "What if someone gets our Root CA private key?" The traditional answer involved manual trust store updates taking months or years. This led to the question: "Why can't a Root CA commit cryptographic suicide?" Further analysis revealed the mathematical paradox: any mechanism that allows CA self-revocation requires the CA's private key to be cryptographically valid. If an attacker possesses this key (the primary threat), they could inadvertently help terminate their own attack by triggering the self-revocation mechanism. This insight has been validated against historical PKI incident timelines, where no comparable solution exists despite numerous high-profile CA compromises. 1.2. Key Innovation The self-revocation mechanism is mathematically secure: it can only be activated by an entity possessing the CA's private key. However, if an attacker gains access to the private key (the primary concern in CA compromise), they would inadvertently help limit their own attack by triggering the self-revocation mechanism. 1.3. Backward Compatibility The extension is designed to be backward compatible with existing PKI infrastructure. Legacy systems that do not recognize the extension will continue to operate normally until the CA issues its final self-revocation CRL. 1.4. Design Philosophy This extension prioritizes mathematical security over operational secrecy: FUNDAMENTAL PRINCIPLE: Security MUST NOT depend on information hiding or access restrictions. All security properties MUST derive from cryptographic primitives and established PKI trust relationships. OPERATIONAL CONVENIENCES: - URL encryption prevents casual discovery during audits - Standardized formats improve implementation consistency - Clear documentation reduces deployment errors SECURITY BOUNDARIES: - Private key possession (cryptographically enforced) - Signature verification (mathematically provable) - Dual-person authorization (procedurally enforced) This design ensures security even when ALL operational details are fully disclosed to potential attackers. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Terminology Certificate Authority (CA): An entity that issues digital certificates. Root CA: A self-signed CA at the top of a certificate hierarchy. Self-Revocation Extension: A certificate extension containing information necessary for the CA to detect compromise signals. Self-Revocation Signal: An external indicator that may trigger the CA's emergency response procedures. Suicide CRL: A Certificate Revocation List (CRL) containing the CA's own certificate serial number, effectively terminating the CA. Monitoring URL: A network location monitored by the CA for potential compromise signals. Dual Person Control (DPC): Security procedure requiring two authorized individuals to complete critical operations. Emergency Signing Key: A cryptographic key used exclusively for authenticating compromise signals, separate from the CA private key. 4. Problem Statement 4.1. Current PKI Vulnerabilities Existing PKI infrastructure suffers from several operational limitations when CAs are compromised: - No automated mechanism for rapid compromise detection - Manual trust store updates can take months or years - Continued certificate issuance during cleanup periods - No standardized method for emergency CA termination 4.2. Historical Incidents 4.2.1. DigiNotar (2011) Timeline Analysis: - June 2011: Initial compromise (undetected) - August 29, 2011: Public disclosure - August 30, 2011: Google Chrome emergency update - September 2, 2011: Mozilla Firefox 6.0.1 release - September 9, 2011: Apple Security Update 2011-005 - September 20, 2011: DigiNotar declared bankrupt Impact: 531 fraudulent certificates issued for 344 domains including Google, Yahoo, Facebook, and CIA.gov. Over 300,000 Iranian users directly affected. Global trust store cleanup required 3+ weeks for major browsers, with embedded systems remaining vulnerable indefinitely. 4.2.2. Symantec Misissuance (2017-2018) - 30,000+ certificates incorrectly issued over multiple years - Google distrusted Symantec CAs starting October 2017 - Multi-year remediation process affecting millions of websites - Complete overhaul required: Symantec sold CA business to DigiCert - Gradual browser distrust implementation through 2018 The Symantec [Symantec] incident demonstrates the long-term impact of CA trust issues on the broader web ecosystem. 4.3. Gap Analysis Current standards (RFC 5280 [RFC5280], RFC 6960 [RFC6960]) provide mechanisms for: - Certificate revocation via CRL - Certificate status checking via OCSP - Trust anchor management However, no standard exists for: - Rapid compromise detection - Emergency CA self-termination - Cryptographically secure CA suicide 4.4. Operational Security Paradox Current PKI implementations exhibit a fundamental operational paradox: significant resources are invested in preventive security measures (HSMs, audits, compliance frameworks) while lacking proportional investment in incident response capabilities. This creates an asymmetric risk profile where: - Prevention: Military-grade procedures and hardware - Response: Manual coordination requiring months - Recovery: Dependent on third-party trust store operators The DigiNotar [DigiNotar] incident exemplifies this paradox: despite industry-standard security controls, the compromise response required 22 days for major browser updates and indefinite periods for embedded systems. During this window, the compromised infrastructure remained fully operational for attackers while being mathematically unusable for legitimate purposes. This specification addresses the operational gap between preventive security investment and proportional incident response capability. Modern PKI infrastructure supports life-critical systems: - Healthcare networks and medical device communications - Emergency services and first responder systems - Military communications and weapons systems - Critical infrastructure (power grids, water systems) - Air traffic control and aviation safety systems Extended compromise periods create unacceptable risk exposure for these systems, where communication integrity can directly impact human safety. 5. Solution Overview 5.1. Architecture The self-revocation mechanism consists of four components: 1. Self-Revocation Extension: Embedded in CA certificates 2. Monitoring Service: Continuously checks for compromise signals 3. Emergency Signing Key: Separate key for signal authentication 4. Manual Authorization: Human-controlled emergency termination Figure 1: Self-Revocation Operational Flow Normal Operation: +---------------------+ +------------------+ +---------------+ | Self-Revocation |--->| Monitoring |--->| Monitoring | | Extension | | Service | | URL | | (in CA certificate) | | (periodic check) | | (encrypted) | +---------------------+ +------------------+ | (no signal) | +---------------+ Emergency Response: +---------------------+ +------------------+ +---------------+ | Emergency Signal |--->| Monitoring |--->| Emergency | | (signed, detected) | | Service | | Response Team | +---------------------+ | (validates) | | (alerted) | +------------------+ +---------------+ | v +---------------------+ +------------------+ +---------------+ | Suicide CRL |<---| Manual CRL |<---| Dual-Person | | (CA terminated) | | Generation | | Authorization | +---------------------+ +------------------+ +---------------+ This architecture separates automated detection from manual authorization, ensuring rapid response while preventing false positive termination. 5.2. Emergency Response Timeline Signal Detection -> Verification -> Authorization -> Distribution (Automated) (Manual) (Manual) (Automated) 0h 15m 45m 1h 2h | | | | | Signal found Team assembly Dual-person Upload to CDP Signature OK Evidence authorization OCSP updates Alert sent verification HSM access Cache flush Compromise CRL generation Verification confirmed Witness log complete Maximum Response Time: 2 hours (vs. months for current manual processes) Timeline Breakdown: - 0-15min: Monitoring service detects and validates emergency signal - 15-45min: Emergency team assembles, verifies evidence, confirms compromise - 45-60min: Dual-person authorization, manual CRL generation with HSM - 1-2h: CRL distribution to all endpoints, OCSP responder updates 5.3. Operational Flow Normal Operation: 1. CA operates normally with embedded self-revocation extension 2. Monitoring service periodically checks monitoring URL 3. No valid signal present: CA continues normal operation Emergency Response: 1. Compromise detected by CA operator or external notification 2. Emergency signal created and signed with emergency signing key 3. Monitoring service detects and validates signal 4. Automated alert to emergency response team 5. Authorized personnel verify compromise evidence 6. Dual-person authorization for emergency termination 7. Manual creation of self-revocation CRL 8. Controlled distribution of suicide CRL to all distribution points 9. CA permanently terminates operations 5.4. Security Properties - Signal detection does not require CA private key - Signal authentication uses separate emergency signing key - CRL generation requires valid CA private key signature - Attackers cannot forge valid suicide CRL without private key - If attackers have private key, termination limits attack duration - No reliance on external trust relationships - Mathematical security based on PKI signature verification 6. Self-Revocation Extension Definition 6.1. Extension Syntax The self-revocation extension is identified by the following OID: id-ce-selfRevocation OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) ds(5) certificateExtension(29) TBD1 } RFC Editor: Please replace TBD1 with the value assigned by IANA [TBD-IANA]. For enterprise-specific implementations during standardization, private OIDs MAY be used temporarily: Example: 1.3.6.1.4.1.44954.1.99.1 (Aviontex GmbH) 6.2. Extension Structure SelfRevocationExtension ::= SEQUENCE { version INTEGER { v1(1) } (v1,...), encryptedData SEQUENCE { encryptedURL OCTET STRING, initializationVector OCTET STRING (12), -- 96 bits for GCM authenticationTag OCTET STRING (16) -- 128 bits for GCM }, keyDerivationSalt OCTET STRING, checkInterval INTEGER OPTIONAL, emergencyContact UTF8String OPTIONAL, signalFormat INTEGER { json(1), xml(2), plain(3) } OPTIONAL, emergencyKeyHash OCTET STRING OPTIONAL -- SHA-256 of emergency public key } 6.3. Extension Semantics encryptedData: Contains AES-256-GCM encrypted monitoring URL with associated cryptographic parameters. The URL MUST use HTTPS and MUST contain sufficient entropy to prevent unauthorized discovery (minimum 384 bits entropy for practical deployment). keyDerivationSalt: Random salt for HKDF-SHA384 key derivation. MUST be cryptographically random with minimum 256 bits entropy. checkInterval: Suggested interval (in seconds) for monitoring the signal URL. Default value is 21600 (6 hours). MUST NOT be less than 3600 (1 hour) for Root CAs. emergencyContact: Contact information for emergency situations. signalFormat: Expected format of the compromise signal for interoperability. emergencyKeyHash: SHA-256 hash of the emergency signing public key used for signal authentication. 6.4. Cryptographic Protection Requirements Root Certificate Authorities implementing this extension MUST use cryptographically protected monitoring URLs to prevent unauthorized discovery and ensure signal integrity. 6.4.1. URL Encryption Process The monitoring URL MUST be encrypted using AES-256-GCM with the following process: 1. Generate cryptographically random salt (256 bits minimum) 2. Generate cryptographically random IV (96 bits for GCM) 3. Derive encryption key using HKDF-SHA384: - Input Key Material (IKM): Root CA public key (DER encoded) - Salt: Random salt from step 1 - Info: "PKI-SUICIDE-URL-v1" || CA Subject Key Identifier - Output Length: 32 bytes (256 bits) 4. Encrypt monitoring URL using AES-256-GCM with derived key and IV 5. Store encrypted URL, IV, authentication tag, and salt in extension 6.4.2. URL Decryption Process CA monitoring services MUST decrypt the monitoring URL using: 1. Extract encrypted data, IV, authentication tag, and salt from extension 2. Derive decryption key using identical HKDF-SHA384 process 3. Decrypt URL using AES-256-GCM with derived key, IV, and tag verification 4. Validate HTTPS URL format and entropy requirements 5. Use decrypted URL for signal monitoring 6.4.3. Security Properties of URL Protection This encryption scheme provides the following security properties: - URL integrity: GCM authentication prevents URL modification - Discovery resistance: Encrypted URLs cannot be trivially extracted - Binding to CA: Key derivation ties URL to specific CA certificate - Signal authentication: Prevents casual false signal placement Note: The encryption provides integrity protection and discovery resistance rather than absolute secrecy, as the decryption key can be derived from the publicly available CA certificate. 6.4.4. URL Protection Design Rationale This extension does NOT attempt to provide absolute URL secrecy. The URL encryption serves specific operational purposes: DESIGN GOALS: * Casual Discovery Prevention: Prevent trivial URL extraction * Integrity Protection: GCM authentication prevents tampering * Format Standardization: Consistent encryption across implementations * Audit Trail: Clear crypto parameters for forensic analysis NOT DESIGN GOALS: * Absolute Secrecy: Any party can derive decryption key * Access Control: URL access remains unrestricted when discovered * Security through Obscurity: System security does not depend on URL secrecy RATIONALE: URL discovery by unauthorized parties does not compromise system security, as valid suicide CRL generation requires CA private key possession. The encryption serves operational purposes rather than fundamental security isolation. This design choice is intentional and mathematically sound. 6.5. Emergency Signing Key Management CAs implementing this extension MUST establish separate emergency signing keys for signal authentication: 6.5.1. Key Generation and Storage Emergency signing keys MUST be: - Generated separately from CA private keys - Stored in air-gapped systems when not in use - Protected with dual-person control access - Rotated at least every 12 months - Backed up in geographically separated secure locations 6.5.2. Supported Algorithms The following signature algorithms are RECOMMENDED for emergency keys: - EdDSA (Ed25519): RECOMMENDED for new deployments - RSA-PSS with SHA-384: ACCEPTABLE for existing infrastructure - ECDSA P-384 with SHA-384: ACCEPTABLE for existing infrastructure 6.5.3. Public Key Distribution Emergency signing public keys MUST be: - Included as SHA-256 hash in emergencyKeyHash field - Distributed to monitoring services through secure channels - Verified against the hash before signal validation - Rotated using secure key rollover procedures 6.6. Signal Format Specification To ensure interoperability, compromise signals MUST follow a standardized format: 6.6.1. JSON Signal Format (RECOMMENDED) { "version": "1.0", "timestamp": "2025-05-30T10:30:00Z", "reason": "private-key-compromise", "evidence": "sha384-hash-of-compromise-evidence", "authorizer": "emergency-response-team", "verification": { "algorithm": "EdDSA", "keyReference": "sha256-hash-of-emergency-pubkey", "signature": "base64-encoded-signature" } } 6.6.2. XML Signal Format (ALTERNATIVE) 1.0 2025-05-30T10:30:00Z private-key-compromise sha384-hash-of-compromise-evidence emergency-response-team base64-encoded-signature 6.6.3. Plain Text Signal Format (MINIMAL) EMERGENCY_REVOCATION_2025-05-30T10:30:00Z_private-key-compromise_ SIGNATURE 6.7. Attack Analysis: Signal Manipulation and CRL Forgery 6.7.1. Scenario: Attacker Discovers Monitoring URL If an attacker discovers the monitoring URL: Attack Vector: Attacker attempts to trigger false compromise signal by creating signal file at the monitored URL. Defense: The compromise signal itself is merely a detection trigger. Actual revocation requires emergency key signature verification, dual-person authorization, and manual creation of a cryptographically valid CRL containing the CA's serial number, signed with the CA's private key. Without the emergency signing key and CA private key, the attacker cannot create a valid suicide CRL that relying parties will accept. Outcome: False signal triggers emergency response procedures but cannot cause actual CA termination without proper authorization and cryptographic keys. 6.7.2. Scenario: Infrastructure Compromise If an attacker compromises the web server hosting the monitoring URL: Attack Vector: Attacker controls the signal endpoint and can create arbitrary signal files. Defense: As above, the signal requires valid emergency key signature. The mathematical security relies on signature verification and CA private key possession, not the web infrastructure. An attacker controlling the URL infrastructure cannot forge the cryptographic signatures required for valid signal authentication or suicide CRL. Outcome: Infrastructure compromise does not affect the actual self-revocation security model. 6.7.3. Scenario: Emergency Key Compromise If an attacker gains access to emergency signing keys: Attack Vector: Attacker creates valid compromise signals to trigger false emergency responses. Defense: Emergency signals trigger human verification procedures, not automatic CRL generation. Dual-person authorization and evidence review prevent false positive termination. Emergency key rotation limits exposure duration. Outcome: False signals increase operational load but cannot cause CA termination without human verification and CA private key access. 6.7.4. Scenario: CRL Forgery Attempts If an attacker attempts to forge a suicide CRL: Attack Vector: Attacker creates a CRL containing the Root CA's serial number and distributes it as a "suicide CRL". Defense: All CRLs MUST be cryptographically signed by the issuing CA's private key. Without access to the Root CA's private key, the attacker cannot create a cryptographically valid signature. Relying parties MUST verify CRL signatures and will reject unsigned or incorrectly signed CRLs. Outcome: Forged CRLs are cryptographically invalid and will be rejected by all standards-compliant implementations. 6.7.5. Scenario: Attacker Possesses CA Private Key If an attacker gains access to the Root CA private key: Attack Vector: Attacker has the capability to issue fraudulent certificates and could potentially create valid suicide CRLs. Analysis: This scenario represents complete CA compromise. In this case, the attacker creating a suicide CRL results in immediate termination of their own attack capability. This creates an optimal outcome from a security perspective: - Without suicide capability: Attack continues indefinitely until manual trust store updates (months/years) - With suicide capability: Attack automatically limited to detection interval (hours) Mathematical Analysis: An attacker with the private key can create valid suicide CRLs, but doing so immediately terminates the CA and prevents further certificate issuance. Outcome: The mathematical property ensures that worst-case compromise scenarios are automatically limited in duration. 7. Implementation Requirements 7.1. Root CA Security Requirements Root Certificate Authorities implementing the Self-Revocation Extension MUST meet enhanced security requirements: 7.1.1. Cryptographic Parameters Root CAs implementing this extension MUST use: - RSA key length: 4096 bits minimum (8192 bits RECOMMENDED) - Hash algorithm: SHA-384 minimum (SHA-512 RECOMMENDED) - Self-Revocation Extension: REQUIRED - URL encryption: AES-256-GCM with HKDF-SHA384 (REQUIRED) - Monitoring interval: Maximum 6 hours (REQUIRED) 7.1.2. Operational Security Root CAs MUST implement: - Dual person control for all private key operations - Hardware Security Module (HSM) protection for private keys - Comprehensive audit logging of all CA operations - Regular security assessments and penetration testing - Incident response procedures with defined roles 7.1.3. Hardware Security Module Requirements Root CAs implementing this extension MUST use HSMs meeting: - FIPS 140-3 [FIPS140-3] Level 3 minimum certification - Dual-person control for all signature operations - Tamper-evident audit logging capabilities - Emergency key destruction procedures - Authenticated firmware with verified boot process 7.2. Emergency Key Infrastructure CAs implementing this extension MUST establish robust emergency key management: 7.2.1. Key Generation Emergency signing keys MUST be: - Generated using certified random number generators - Created in air-gapped environments - Witnessed by authorized personnel during generation - Immediately stored in secure hardware tokens 7.2.2. Key Storage and Access Emergency keys MUST be: - Stored in geographically separated locations - Protected with dual-custody access controls - Regularly tested for integrity and availability - Backed up using secure key escrow procedures 7.2.3. Key Rotation Emergency keys MUST be: - Rotated at least every 12 months - Immediately rotated upon suspected compromise - Replaced using secure key rollover procedures - Verified for proper function before activation 7.3. CA Implementation Requirements CAs implementing this extension MUST: - Include the encrypted self-revocation extension in CA certificates - Implement monitoring service for the decrypted monitoring URL - Maintain dual-person control for emergency procedures - Generate valid suicide CRL only with proper authorization - Distribute suicide CRL to all certificate distribution points - Implement secure private key destruction procedures - Maintain empty CRL generation for normal operations - Ensure monitoring service availability (99.9% uptime minimum) 7.4. Automation Prohibition Root Certificate Authorities implementing this extension MUST NOT automate suicide CRL generation to prevent catastrophic false positive scenarios. 7.4.1. REQUIRED Manual Processes The following processes MUST be performed manually: - Human verification of compromise evidence - Dual-person authorization (minimum 2 authorized staff) - Manual CRL generation with witness protocol - Manual distribution with verification checkpoints - Documented decision trail with digital signatures 7.4.2. FORBIDDEN Automated Processes The following processes MUST NOT be automated: - Automatic CRL generation upon signal detection - Script-based emergency procedures without human oversight - Unattended suicide activation mechanisms - Single-person emergency authorization workflows 7.4.3. Rationale for Manual Control False positive suicide CRL generation represents catastrophic operational risk affecting millions of certificates and critical infrastructure. The gravity of CA termination demands human judgment and dual-person control consistent with existing PKI operational standards and regulatory requirements. Historical precedent: No critical infrastructure system (nuclear, military, aviation) implements fully automated emergency shutdown without human oversight and dual-person authorization. 8. Operational Procedures 8.1. Normal Operations During normal CA operations: 1. CA operates normally with embedded self-revocation extension 2. Monitoring service checks monitoring URL at configured interval 3. No valid signal present: CA continues normal operation 4. Log monitoring activities for audit purposes 5. Maintain monitoring service availability and redundancy 6. Update empty CRLs according to baseline requirements 7. Rotate emergency keys according to schedule 8.2. Signal Detection and Verification When monitoring service detects a potential compromise signal: 1. Automated download and format validation of signal 2. Emergency key signature verification against known public key 3. Signal timestamp and freshness validation 4. Preliminary assessment of signal authenticity 5. Automated alert to emergency response team 6. Documentation of detection event with complete audit trail 8.3. Emergency Authorization Process Upon valid signal verification: 1. Assembly of minimum two authorized personnel 2. Review of compromise evidence referenced in signal 3. Verification of emergency authorization credentials 4. Independent confirmation of compromise through additional sources 5. Dual-person approval for suicide CRL generation 6. Documentation of authorization decision with digital signatures 8.4. Manual CRL Generation For authorized emergency termination: 1. Physical presence of both authorized personnel required 2. Secure access to CA private key (HSM dual-key procedure) 3. Manual generation of suicide CRL containing CA serial number 4. Verification of CRL format and digital signature 5. Secure logging of CRL generation with witness attestation 6. Creation of multiple copies for distribution redundancy 8.5. Distribution and Verification Following suicide CRL creation: 1. Manual upload to all CRL distribution points 2. Verification of successful propagation to all mirrors 3. Update of OCSP responders with revocation status 4. Cache invalidation commands to all CDN endpoints 5. Notification to trust store operators 6. Monitoring of client adoption and response 7. Documentation of distribution completion 8.6. Post-Revocation Procedures After successful self-revocation: 1. Secure destruction of all CA private key material 2. Destruction of emergency signing keys 3. Coordination with trust store operators for CA removal 4. Communication to affected certificate holders 5. Public notification of CA termination 6. Establishment of successor CA infrastructure if required 7. Comprehensive post-incident analysis and documentation 8. Regulatory notification as required by jurisdiction 9. Security Considerations 9.1. Fundamental Security Principle The core security principle of this mechanism is mathematically sound: CA termination can only be triggered by entities possessing the CA's private key for CRL generation. This creates a security model where compromise attempts become self-limiting. 9.2. Threat Model Analysis 9.2.1. Attacker Without CA Private Key If an attacker gains access to CA infrastructure but not the private key, they cannot: - Generate valid suicide CRL (requires private key signature) - Forge self-revocation signals (requires emergency key signature) - Cause CA termination through false signals (requires human verification) - Issue valid certificates (existing PKI limitation) Impact: No security degradation beyond current PKI standards. The self-revocation mechanism provides no additional attack surface. 9.2.2. Attacker With Emergency Signing Key Only If an attacker gains access to emergency signing keys but not the CA private key, they can: - Create valid compromise signals - Trigger emergency response procedures - Cause operational disruption through false alarms But they cannot: - Generate valid suicide CRL (requires CA private key) - Actually terminate the CA without human authorization - Bypass dual-person control procedures Impact: Operational disruption but no security compromise. Regular key rotation limits exposure duration. 9.2.3. Attacker With CA Private Key If an attacker gains access to the CA private key, they can: - Issue fraudulent certificates (existing PKI vulnerability) - Generate valid suicide CRL (beneficial security outcome) - Process legitimate self-revocation signals (beneficial outcome) Analysis: In this scenario, the attacker triggering the suicide mechanism produces an optimal security outcome. The alternative (attacker having private key but not triggering suicide) would result in indefinite certificate fraud capability. Impact: Attack duration limited to maximum check interval versus months/years under current standards. 9.2.4. Economic Incentive Analysis Attackers who obtain CA private keys typically seek to: - Issue fraudulent certificates for profit - Maintain long-term access for ongoing exploitation - Avoid detection to maximize return on investment Self-revocation creates an economic disincentive for attackers to trigger termination, as doing so immediately destroys their ability to monetize the compromise. However, if termination is triggered, it represents the optimal damage limitation scenario. 9.3. Operational Security Organizations implementing this extension should: - Implement robust access controls for signal infrastructure - Maintain secure backup and recovery procedures - Establish comprehensive emergency contact procedures - Conduct regular testing of detection procedures (not termination) - Monitor signal infrastructure availability and integrity - Implement comprehensive audit logging for all operations 9.4. Privacy and Confidentiality The encrypted self-revocation URL is embedded in publicly accessible certificates. Organizations should: - Use AES-256-GCM encryption for URL protection - Implement appropriate access logging on monitoring endpoints - Ensure URL encryption parameters are properly managed - Consider URL rotation strategies for enhanced security - Monitor for unauthorized access attempts Privacy Impact: URL encryption prevents casual observation of monitoring infrastructure while allowing authorized monitoring services to function correctly. 9.5. Cryptographic Security The security of this mechanism relies on: - Asymmetric cryptography (RSA/ECDSA) for CRL signatures - Emergency key signatures for signal authentication - CA private key secrecy (same assumption as existing PKI) - Symmetric encryption (AES-256-GCM) for URL protection - No additional cryptographic assumptions beyond current PKI Key Insight: This mechanism does not weaken existing PKI security in any scenario. It either maintains current security levels (when private key is secure) or significantly improves them (when private key is compromised). 9.6. Frequently Misunderstood Design Decisions 9.6.1. "Why can anyone decrypt the URL?" The URL encryption key can be derived by any party possessing the CA certificate (which is public). This is INTENTIONAL design: - Monitoring services need URL access without private key possession - Security does not rely on URL secrecy - False signals cannot cause harm without private key - Discovered URLs create no additional attack surface 9.6.2. "Isn't this security through obscurity?" NO. The security model relies on: - Cryptographic signature verification (RSA/ECDSA) - Private key possession requirements - Dual-person authorization procedures - Mathematical impossibility of CRL forgery URL obfuscation is an operational convenience, not a security boundary. 9.6.3. "What if attackers find all monitoring URLs?" IRRELEVANT. Attackers discovering monitoring URLs can: - Set false signals (harmless without emergency key signature) - Monitor CA status (information already public) - DoS monitoring infrastructure (operational issue, not security breach) Attackers CANNOT: - Force valid suicide CRL generation without private key - Bypass dual-person authorization requirements - Forge cryptographically valid signatures The system remains mathematically secure regardless of URL discovery. 9.6.4. "What about false positive termination?" False positive termination is prevented by: - Emergency key signature requirement for valid signals - Dual-person authorization for all CRL generation - Human verification of compromise evidence - Comprehensive audit trails for accountability The probability of false positive termination approaches zero with proper implementation of manual controls. 10. IANA Considerations 10.1. Object Identifier Allocation This document requests IANA to allocate an object identifier for the self-revocation extension under the Certificate Extensions arc: id-ce-selfRevocation OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) ds(5) certificateExtension(29) TBD1 } RFC Editor: Please replace TBD1 with the value assigned by IANA [TBD-IANA]. 10.2. Self-Revocation Extension Registry IANA is requested to create a new registry for self-revocation extension parameters: Registry Name: PKI Self-Revocation Extension Parameters Registration Procedure: Specification Required with Expert Review Reference: This document Initial registry entries: - Version numbers (1-255) - Signal format identifiers (1-255) - Cryptographic algorithm identifiers 10.3. Signal Format Registry IANA is requested to create a registry for standardized signal formats: Registry Name: PKI Self-Revocation Signal Formats Registration Procedure: First Come First Served Reference: This document Initial formats: - JSON (1): Structured signal with metadata - XML (2): Structured signal in XML format - Plain (3): Simple text-based signal 11. Deployment Considerations 11.1. Migration Timeline Implementation of self-revocation extensions should follow a measured deployment timeline: Phase 1 (Months 1-6): Specification finalization and tooling development - Complete IETF standardization process - Develop reference implementations - Create testing and validation tools - Establish certification procedures Phase 2 (Months 7-12): Pilot deployments with early adopter CAs - Limited deployment with volunteer CAs - Real-world testing in controlled environments - Feedback collection and specification refinement - Training development for operational staff Phase 3 (Months 13-24): Broader CA implementation and testing - Wider adoption by progressive CAs - Integration with existing PKI infrastructure - Comprehensive interoperability testing - Development of best practices documentation 11.2. Backward Compatibility Strategy During deployment: - Legacy systems will ignore unknown extensions (standard behavior) - CRL processing remains fully compatible with existing implementations - OCSP integration maintains current protocol compliance - Gradual adoption does not disrupt existing PKI operations - Monitoring can be implemented without affecting certificate issuance 11.3. Cost-Benefit Analysis Organizations should consider: Implementation Costs: - Emergency key infrastructure development - Monitoring system deployment and maintenance - Staff training for emergency procedures - Compliance and audit system updates Security Benefits: - Dramatic reduction in compromise exposure time - Improved incident response capabilities - Enhanced trust store operator confidence - Reduced liability exposure from extended compromises The security benefits significantly outweigh implementation costs for any CA serving critical infrastructure or high-value applications. 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 12.2. Informative References [DigiNotar] Fox-IT, "DigiNotar Certificate Authority breach - Operation Black Tulip", September 2011, . [FIPS140-3] National Institute of Standards and Technology, "Security Requirements for Cryptographic Modules", FIPS PUB 140-3, March 2019, . [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., Galperin, S., and C. Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP", RFC 6960, DOI 10.17487/RFC6960, June 2013, . [Symantec] Sleevi, R., "Chrome's Plan to Distrust Symantec Certificates", Google Security Blog, March 2017, . [TBD-IANA] IANA, "Object Identifier Arcs", . Appendix A. Implementation Examples A.1. OpenSSL Configuration Example Example OpenSSL configuration for including self-revocation extension: [ ca_extensions ] basicConstraints = critical,CA:TRUE,pathlen:1 keyUsage = critical,keyCertSign,cRLSign subjectKeyIdentifier = hash # Self-Revocation Extension (using temporary private OID) 1.3.6.1.4.1.44954.1.99.1 = ASN1:SEQUENCE:self_revocation_ext [ self_revocation_ext ] version = INT:1 encryptedData = SEQUENCE:encrypted_data_seq keyDerivationSalt = FORMAT:HEX,OCTETSTRING:9A3C7E0F2D4B8A6C... checkInterval = INT:21600 emergencyContact = UTF8:emergency@aviontex.com signalFormat = INT:1 emergencyKeyHash = FORMAT:HEX,OCTETSTRING:A7B3C9E1F4D2B8A6... [ encrypted_data_seq ] encryptedURL = FORMAT:HEX,OCTETSTRING:4F8A2E1D9C7B6A5E... initializationVector = FORMAT:HEX,OCTETSTRING:2E4A8C6F1D5B9A3C... authenticationTag = FORMAT:HEX,OCTETSTRING:7F3E9A1C5D8B2F4A... A.2. Emergency Response Procedure Example emergency response checklist: 1. Signal Detection Verification - [ ] Confirm signal presence at monitoring URL - [ ] Validate signal format and digital signature - [ ] Verify signal timestamp and freshness (< 24 hours) - [ ] Cross-reference with internal security monitoring - [ ] Document detection time and circumstances 2. Emergency Authorization - [ ] Assemble minimum two authorized personnel - [ ] Verify identity of responding personnel (biometric/badge) - [ ] Review evidence referenced in compromise signal - [ ] Obtain independent confirmation of compromise - [ ] Obtain dual authorization for termination - [ ] Document authorization decision with signatures 3. Manual CRL Generation - [ ] Access secure CA environment with dual control - [ ] Verify HSM functionality and key availability - [ ] Generate suicide CRL with CA serial number - [ ] Verify CRL digital signature and format - [ ] Create backup copies for distribution - [ ] Log CRL generation with witness signatures 4. Distribution and Cleanup - [ ] Upload CRL to all distribution points - [ ] Verify propagation to all mirror locations - [ ] Update OCSP responders with revocation status - [ ] Invalidate all caches (CDN, browser, application) - [ ] Notify trust store operators via emergency contacts - [ ] Initiate private key destruction procedures - [ ] Begin successor CA planning if required 5. Post-Incident Activities - [ ] Conduct comprehensive forensic analysis - [ ] Document lessons learned and process improvements - [ ] Update emergency procedures based on experience - [ ] Coordinate with law enforcement if required - [ ] Prepare public disclosure and communication Author's Address Torsten Jahnke Chief Executive Officer Aviontex GmbH - keweonDNS Project Bavaria, Germany Email: torsten.jahnke@aviontex.de URI: https://www.aviontex.de Acknowledgments This work was developed as part of security enhancements for the keweonDNS project at Aviontex GmbH. The authors acknowledge the contributions of the PKI security community in identifying the operational gaps that this specification addresses. Special thanks to the security researchers and PKI experts who provided detailed technical review and identified critical implementation considerations that significantly improved the robustness and security of this specification. The historical analysis of PKI compromise incidents was informed by public reports from Fox-IT, Google Security Team, Mozilla Security Team, and various academic security researchers who documented the operational challenges in existing PKI infrastructure.