Standards

Chapter 9 / 15

Post-Quantum Signatures

pq_key, @pq_signed — Dilithium-5 authentication.

Classical ECDSA signatures are vulnerable to sufficiently large quantum computers. Covenant adds pq_key<Scheme> as a first-class storage type and @pq_signed as a decorator that verifies post-quantum signatures at function entry. The verification compiles to a STATICCALL into the chain's PQ precompile (0x0400–0x0401).

pq_vault.cov
record PQVault {
    // Store a Dilithium-5 public key instead of an address
    pq_owner:  pq_key;
    balance:   amount;
    nonce:     u64;

    error BadSignature();

    // @pq_signed verifies the caller's Dilithium-5 signature over
    // (contract_address ++ nonce ++ calldata) before the body runs
    @pq_signed(self.pq_owner)
    action withdraw(to: address, value: amount) {
        if value > self.balance {
            revert_with InsufficientFunds(value, self.balance);
        }
        self.balance -= value;
        self.nonce   += 1;
        transfer(to, value);
    }

    // Standard ECDSA deposit — anyone can fund
    action deposit() {
        self.balance += msg.value;
    }

    error InsufficientFunds(requested: amount, available: amount);
}
hybrid_auth.cov — ECDSA + PQ dual key
record HybridWallet {
    // Both keys must sign for high-value ops
    classical_owner: address;
    pq_owner:        pq_key;
    threshold:       amount;

    // Small withdrawals: classical ECDSA only
    action withdraw_small(to: address, value: amount)
        only(self.classical_owner)
        when(value <= self.threshold)
    {
        transfer(to, value);
    }

    // Large withdrawals: require PQ signature too
    @pq_signed(self.pq_owner)
    action withdraw_large(to: address, value: amount)
        only(self.classical_owner)
        when(value > self.threshold)
    {
        transfer(to, value);
    }
}

Annotations

pq_key<Dilithium5>stores a Dilithium-5 public key (NIST FIPS 204 Level 5). The key is stored as bytes in EVM storage.
@pq_signed(key)prepends a STATICCALL to precompile 0x0400 that verifies the signature over the canonical message keccak256(address ++ nonce ++ selector ++ calldata).
Supported schemesDilithium3 (NIST Level 3), Dilithium5 (NIST Level 5), Falcon512, Falcon1024. Chain support varies.
Nonceis automatically incremented by the PQ precompile to prevent replay attacks — you don't manage it manually.

Key takeaways