Zama (FHE)

Zama provides Fully Homomorphic Encryption (FHE), enabling computation on encrypted data without ever decrypting it. In Delibera, this will enable blind voting -- the coordinator can tally votes without learning how any individual worker voted.

What Is FHE?

Traditional encryption requires decryption before processing. FHE allows arithmetic operations directly on ciphertext:

encrypt(a) + encrypt(b) = encrypt(a + b)

The result is still encrypted. Only the key holder can decrypt the final tally.

TFHE Scheme

Zama uses the TFHE (Torus Fully Homomorphic Encryption) scheme, optimized for boolean and small-integer operations -- a natural fit for vote tallying.

| Property | Value | |---|---| | Scheme | TFHE | | Operations | Boolean gates, integer arithmetic | | Use case | Vote encryption and homomorphic tallying | | Decryption | Only by designated key holder (coordinator or threshold) |

Planned Architecture

1. Each worker encrypts its vote using the FHE public key
2. Encrypted votes are submitted to the coordinator
3. The coordinator performs homomorphic addition over all encrypted votes
4. The final encrypted tally is decrypted to reveal only the aggregate result

Worker 1: encrypt(vote_1) --\
Worker 2: encrypt(vote_2) ---+--> homomorphic_sum --> decrypt --> tally
Worker 3: encrypt(vote_3) --/

Individual votes are never visible to the coordinator, other workers, or any observer. Only the aggregate outcome is revealed.

Privacy Guarantees

• Individual vote privacy -- No party learns how a specific worker voted
• Tally integrity -- The homomorphic property ensures the tally is mathematically correct
• No trusted third party -- Unlike current Ensue-based voting, FHE removes the need to trust the coordination layer with plaintext votes