LP-043: Key VM

Abstract

The Key VM runs the K-chain, a dedicated chain for the key lifecycle:

distributed key generation, share distribution, encryption at rest, rotation,

and retirement. It is the cold path of the network's cryptographic state.

The T-chain (Threshold VM) is the hot path that uses these keys for actual

signing.

Precompile address nibble: C=9 (see LP-129 Registry).

Scope — what K-chain owns

• Key creation across all supported schemes (ML-KEM, ML-DSA, BLS,

secp256k1, Ed25519)

• Distributed key generation (DKG) orchestration — feeds into T-chain sessions
• Key share encryption using per-validator ML-KEM transport keys
• Key retirement and re-share on validator set changes
• Key-usage audit log (every signing session references the key record)

Scope — what K-chain does NOT own

• Signing session execution (T-chain / Threshold VM)
• Identity keys / DID material (I-chain / Identity VM)
• Validator staking keys (P-chain / Platform VM)

Separation from T-chain

The split is driven by different security properties:

• K-chain is cold path: infrequent operations, high security, long-term state.
• T-chain is hot path: many short-lived sessions, availability matters.

Merging them forces hot-path availability guarantees on cold-path state,

which is both expensive and wrong.

Key Record

type KeyRecord struct {
    ID              [32]byte
    Scheme          KeyScheme       // MLKEM | MLDSA | BLS | SECP256K1 | ED25519
    Threshold       Threshold       // (T, N) tuple, or (1,1) for single-party
    PublicKey       []byte
    ShareCommitments [][]byte        // One commitment per participating validator
    CreatedAt       uint64          // Block timestamp
    Status          Status          // Active | Rotating | Retired
    Policy          UsagePolicy     // Max signings per epoch, allowed contexts
}

DKG Flow

1. K-chain accepts a CreateKeyTx from an authorized principal

2. K-chain selects the committee (see LP-044 Threshold VM for committee selection)

3. Committee runs DKG off-chain, publishes share commitments on K-chain

4. K-chain verifies commitments, creates KeyRecord, sets Status=Active

5. Key becomes available for use via T-chain signing sessions

Rotation

Rotation is a fresh DKG that preserves the public key but redistributes shares.

Triggered by:

• Validator set change (automatic on epoch boundary)
• Policy violation (detected by T-chain surveillance)
• Manual rotation request (authorized principal)

Audit

Every SignSession on T-chain references a KeyRecord.ID. K-chain surfaces

a queryable audit log: which keys signed what, when, at whose request. This

is NOT the hot path — callers read from T-chain for real-time sessions;

K-chain is the archive.

Reference