Quantum Resistant Integrity Strategy

Context

The integrity of the voting engine and legislative records is the core value proposition of TrustVote AI. While SHA-256 is the current industry standard, it faces significant security degradation due to Grover's Algorithm as quantum computing advances. To fulfill our promise of a "Decadal-Scale" high integrity system, we must implement a hashing strategy that remains robust in a post-quantum (PQ) landscape.

Comparison (Integrity Standards)

Algorithm	Digest Size	Quantum Resistance	Performance	Standard
SHA-256	256 bits	Medium (128 bits effective)	High	Legacy Standard
SHA-512	512 bits	High (256 bits effective)	High (64-bit arch)	Modern Standard
SHA3-512	512 bits	High (256 bits effective)	Medium	NIST (FIPS 202)
BLAKE3	256/512 bits	High	Extreme	Emerging

Decision

We will implement SHA3-512 for all document and vote hashing. Furthermore, we will architect the voting engine to utilize a Merkle Tree structure for block-level integrity verification.

Rationale

1. SHA3-512 (NIST FIPS 202): Unlike the SHA-2 family, SHA-3 is based on the "Sponge" construction. It is structurally immune to certain classical attacks (like length extension) and provides a superior security margin against quantum-enabled collision searches.
2. Standardization vs. Performance (Why not BLAKE3?): While BLAKE3 offers superior performance, SHA3-512 was chosen because it is an official NIST Standard. For a project centered on "Trust" and government grade auditing, using a FIPS compliant algorithm provides higher institutional credibility and easier regulatory approval than an emerging (though secure) alternative.
3. 256-bit Post-Quantum Security: By utilizing a 512-bit digest, even when halved by Grover's Algorithm, we maintain 256 bits of effective security—making brute-force attacks computationally infeasible for the foreseeable future.
4. Merkle Tree Integration: Transitioning from isolated hashes to an interconnected tree structure ensures that any modification to a single vote will invalidate the "Root Hash" of the entire ledger. This allows for rapid, lightweight auditing of massive datasets.

Consequences

• Storage Expansion: The hash field in our database must be expanded to 128 characters (Hex) or 64 bytes (Binary).
• DB Schema Update: The votes and legislative_docs tables must be updated to accommodate the larger digest size.
• Node.js Integration: We will leverage the native node:crypto module, ensuring zero external dependencies for our core security logic.
• CPU Overhead: While SHA-3 is slightly more CPU-intensive than SHA-256, the high-throughput nature of the Fastify engine and modern server hardware renders the latency impact negligible.

Next Steps

• Refactor schema.ts to support 512-bit hashes.
• Implement SecurityService for SHA3-512 generation.
• Design the Merkle Tree chaining logic for the voting engine.