Add enhanced NIZK proof context binding (2026/01 datatype)#468
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Add enhanced NIZK proof context binding (2026/01 datatype)#468
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This enhancement cryptographically binds NIZK proofs to their specific
context within an election, preventing proof transplantation attacks
where proofs could theoretically be reused across different elections,
questions, or voters.
Key changes:
- Upgrade from SHA-1 to SHA-256 for challenge generation
- Add ProofContext class to bind proofs to election/question/answer/voter
- New datatype version: 2026/01/Election
- Challenge reduced mod q (required since SHA-256 can exceed q)
- Full backward compatibility with legacy elections (SHA-1)
Context binding format:
election:{hash}|question:{index}|answer:{index}|voter:{alias}
Files:
- helios/crypto/algs.py: ProofContext class, SHA-256 generators
- helios/workflows/homomorphic.py: Context-aware proof gen/verify
- helios/datatypes/2026/01.py: New datatype definitions
- helios/media/helios/jscrypto/*.js: JavaScript implementation
- docs/crypto/context-binding.md: Technical documentation
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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THIS IS A DRAFT
This enhancement cryptographically binds NIZK proofs to their specific context within an election, preventing proof transplantation attacks where proofs could theoretically be reused across different elections, questions, or voters.
Key changes:
Context binding format:
election:{hash}|question:{index}|answer:{index}|voter:{alias}
Files:
🤖 Generated with Claude Code