midnight-cryptography

Midnight Node Cryptography

Outside the Midnight Ledger (which has its own ZK circuits), the Midnight node relies on foundational cryptographic algorithms for consensus, state transition integrity, and network communication.

Algorithm map

flowchart TB
  subgraph Hash["Hashing"]
    B2["Blake2-256 — cryptographic"]
    T2["twoxhash — non-cryptographic storage keys"]
  end

  subgraph Sign["Signature schemes"]
    SR["sr25519 — AURA block authorship"]
    ECDSA["ECDSA — Partnerchain consensus messages"]
    ED["Ed25519 — GRANDPA finality + libp2p"]
  end

subgraph Use["Used for"] B2 --> Blocks["Block hashes, state transitions"] T2 --> Trie["Patricia-Merkle trie key generation"] SR --> AURA["AURA block production"] ECDSA --> PC["Partnerchain coordination"] ED --> GRANDPA["GRANDPA votes"] ED --> P2P["libp2p protocol messages"] end

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## Blake2-256 (primary hash)

**Blake2-256** is the primary cryptographic hash function on Midnight.

- Used for **block hashes** and general-purpose hashing in state transition functions.
- Balances **performance** and **security** for runtime-critical operations.

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## Signature schemes

Midnight uses **three distinct schemes** depending on role:

| Scheme | Construction / basis | Used for |
|--------|---------------------|----------|
| **sr25519** | Schnorrkel + Ristretto x25519 | Signing **AURA block authorship** messages |
| **ECDSA** | Standard elliptic-curve ECDSA | Signing **Partnerchain-related consensus** messages (external interoperability) |
| **Ed25519** | Edwards-curve EdDSA | **GRANDPA finality** messages and **libp2p** protocol messages |

```mermaid
flowchart LR
  subgraph Consensus
    AURA["AURA slot"] -->|sr25519| BA["Block authorship"]
    GRANDPA["GRANDPA vote"] -->|Ed25519| FV["Finality message"]
    PC["Partnerchain signal"] -->|ECDSA| PM["Cross-chain message"]
  end

  subgraph Network
    L2P["libp2p handshake"] -->|Ed25519| PI["Peer identity separate from consensus keys"]
  end

sr25519

• Efficient key derivation and signature aggregation.
• Strong security guarantees for Substrate-style block production.

ECDSA

• Ensures interoperability with systems where ECDSA is the standard (Partnerchain / Cardano ecosystem bridges).

Ed25519

• Fast verification for high-frequency validator communication during finalization.
• Also used for libp2p peer identity (separate keypair from consensus signing keys).

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twoxhash (storage keys)

twoxhash is a non-cryptographic hash used to generate storage keys in the Patricia-Merkle trie.

• Optimized for speed and low collision rates.
• Not suitable for security-sensitive hashing.
• Significantly improves trie lookup performance.

See midnight-storage/ for how twoxhash fits into ParityDB and state commitments.

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Ledger vs node crypto

Layer	Cryptography
Midnight Ledger	ZK proofs, ZSwap circuits, contract proof verification
Midnight Node	Blake2-256, sr25519, ECDSA, Ed25519, twoxhash

Do not conflate ledger proof verification (handled by pallet-midnight) with node-level consensus and P2P primitives.

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Related skills

• midnight-consensus/ — which schemes sign AURA vs GRANDPA vs Partnerchain messages
• midnight-storage/ — twoxhash in trie key generation
• midnight-p2p-networking/ — Ed25519 peer identity in libp2p