Cryptography
ULedger's tamper-evidence guarantees rest on three cryptographic layers: signature schemes (who authorized each action), Merkle chaining (ordering and integrity of blocks), and STARK proofs (compact, verifiable history across epochs).
Signature Schemes
Each chain is created with a fixed key algorithm. All wallets on that chain use the same algorithm.
| Algorithm | Type | Quantum-safe | Notes |
|---|---|---|---|
secp256k1 | ECDSA | No | Standard Bitcoin/Ethereum curve. Widely supported. |
ed25519 | EdDSA | No | Compact signatures, fast verification. |
bls12377 | BLS pairing-based | No | Enables signature aggregation. |
mldsa87 | ML-DSA-87 (Dilithium-5) | Yes | Post-quantum. Required for long-term tamper evidence. |
mldsa87 (ML-DSA-87) is the CRYSTALS-Dilithium variant at NIST security level 5, implemented via Cloudflare CIRCL. It is the algorithm of choice for agent wallet deployments where the audit trail must be verifiable after quantum computers are viable.
Key Derivation
Wallet private keys are derived from BIP39 mnemonics with entropy. The .ukey file stores the private key; it never leaves the SDK. Only the public key and signed transactions touch the network.
Address derivation:
address = SHA-256(lowercase(publicKeyHex))
Merkle Chaining
Each block header includes the Merkle root of all transactions in that block and a hash pointer to the prior block header. This creates an append-only chain: altering any transaction invalidates all subsequent block hashes.
STARK Proofs (Helix)
The Helix sidecar runs per node and produces Plonky3 STARK proofs over epoch batches of blocks. Properties:
| Property | Detail |
|---|---|
| Proof system | Plonky3 (STARK, no trusted setup) |
| Epoch coverage | Each proof covers a batch of block headers and member data |
| Recursive folding | Each epoch proof folds into the prior proof chain |
| Result | A constant-size proof over arbitrary chain history |
| Cross-algorithm anchoring | Checkpoints signed by both secp256k1 and mldsa87 council members |
An independent auditor can verify the entire chain history using only the checkpoint proofs and the council's public keys. No access to any live node is required.
Zero-Knowledge Proofs
For cross-chain anchoring (cross-Merkleization), ULedger uses ZK-SNARK proofs (Groth16 and PLONK variants) to validate cross-chain state references without revealing the underlying data.
Detailed References
- Cryptographic Foundation (Glossary) - hash functions, ZK proof systems, algorithm implementation notes
- Cross-Merkleization (Glossary) - multi-chain proof anchoring
- Helix: STARK Proof System - Plonky3 pipeline, recursive folding, independent auditor workflow
- Wallet Key Types