Script System

Tidecoin inherits the Bitcoin Core script engine and extends it for post-quantum transaction validation. Existing script templates remain available, while the post-AuxPoW ruleset adds strict PQ signature verification, witness v1 P2WSH-512, and OP_SHA512.

This page is the canonical script behavior summary. It is not an address tutorial; for address encoding, see Address Formats. It is not the signature scheme registry; for scheme prefixes and sizes, see Scheme Registry.

Activation status

On testnet, AuxPoW activates at height 1000. On regtest, it is active from height 0. On mainnet, AuxPoW is currently disabled.

Common script templates

Key-hash templates commit to HASH160(serialized_pq_public_key). The serialized PQ public key includes the one-byte scheme prefix.

PQ signature checks

OP_CHECKSIG and related signature-checking paths verify post-quantum signatures through Tidecoin’s PQ public-key dispatch. The serialized public key selects the scheme:

scheme_prefix || raw_scheme_public_key

The signature stack item contains the scheme signature plus the normal sighash byte when the script path uses one:

scheme_signature || sighash_type

Before AuxPoW activation, consensus allows Falcon-512 under the legacy verification regime. At and after AuxPoW activation, SCRIPT_VERIFY_PQ_STRICT is enabled and new spends must satisfy strict PQ verification.

OP_SHA512

OP_SHA512 is opcode 0xb3.

When SCRIPT_VERIFY_SHA512 is active, OP_SHA512:

1. Requires at least one stack item.
2. Removes the top stack item.
3. Computes SHA-512 over that item.
4. Pushes the 64-byte digest.

Before SCRIPT_VERIFY_SHA512 is active, OP_SHA512 is treated as an upgrade-reserved opcode by the normal script flag rules. If SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS is active while SHA-512 is not enabled, use of the opcode is rejected as an upgradable-NOP violation.

Witness v1 P2WSH-512

Witness v1 P2WSH-512 uses this output script:

OP_1 <64-byte SHA512(witness_script)>

Validation rules:

1. SCRIPT_VERIFY_WITNESS_V1_512 must be active.
2. The witness program must be exactly 64 bytes.
3. The witness stack must not be empty.
4. The last witness stack item is interpreted as the witness script.
5. The node computes SHA512(witness_script) and compares it with the 64-byte witness program.
6. If the hash matches, the witness script executes under SigVersion::WITNESS_V1_512.

When witness v1 is not active, version-1 witness programs are handled by the normal upgradable witness-program rules rather than by P2WSH-512 execution.

Script verification flags

Validation adds all three flags once the block height is at or after nAuxpowStartHeight.

Standardness limits

Tidecoin keeps Bitcoin-style policy boundaries while increasing some P2WSH limits for larger PQ scripts:

These are relay and mining policy limits, not all consensus limits. A transaction can be consensus-valid while still non-standard for mempool relay.

Source of truth

See also: Witness V1 SHA-512, Transactions, Address Formats, Verification Modes.