E2EE Security Audit: Industry-Standard Encryption Verified

cybersecurity · 2026-08-31

Comprehensive security audit of BlackVoice Technologies' E2EE implementation confirming industry-standard encryption with X3DH, Double Ratchet, and AES-256-GCM.

## Executive Summary BlackVoice Technologies' End-to-End Encryption (E2EE) implementation has undergone a comprehensive security audit. **Status: Implementation Correct** - following industry standards with proper cryptographic primitives. The server CANNOT decrypt messages - all encryption/decryption happens exclusively on the client device. --- ## 1. Key Agreement Protocol (X3DH) ### Implementation: Correct **Algorithms Used:** - **ECDH P-256** for Diffie-Hellman key exchange - **ECDSA P-256** for digital signatures - **HKDF-SHA256** for key derivation **X3DH Flow:** ``` IKa (Identity Key A) + EKa (Ephemeral Key A) ↓ DH with IKb (Identity Key B) + SPKb (Signed PreKey B) + OPKb (One-Time PreKey B) ↓ DH1 = DH(IKa, SPKb) - Authentication DH2 = DH(EKa, IKb) - Forward secrecy DH3 = DH(EKa, SPKb) - Forward secrecy DH4 = DH(EKa, OPKb) - Extra forward secrecy (optional) ↓ SharedSecret = HKDF(DH1 || DH2 || DH3 || DH4) ``` **Security Verifications:** - SignedPreKey signature is verified before handshake - Explicit error on failed verification: "potential MITM attack" - One-Time PreKeys are deleted after use - Session nonce derived from transcript for binding --- ## 2. Double Ratchet (Perfect Forward Secrecy) ### Implementation: Correct (Protocol v8) **Components:** - Root Key (32 bytes) - evolves with each DH ratchet - DH Key Pairs - ephemeral keys for each ratchet step - Chain Keys - separate for send/receive directions - Message Counters - prevent replay attacks - Skipped Message Keys - handle out-of-order delivery - Epoch tracking - session synchronization **Per-Message Key Rotation:** ``` MessageKey[n] = HKDF(ChainKey[n-1], "message") ChainKey[n] = HKDF(ChainKey[n-1], "chain") ``` **Forward Secrecy Verified:** - New ephemeral key at each DH ratchet - Root key evolves after each DH ratchet - Message keys cannot be calculated backwards - Past messages stay secure even if current keys are compromised --- ## 3. Message Encryption (AES-256-GCM) ### Implementation: Correct **

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