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zeekay
9c9106017e
The single place a Lux cross-chain atomic swap is constructed across all three legs, composed from one shared primitive: - secret.go — Secret [32]byte, Hashlock() = sha256(secret), constant-time VerifyPreimage. THE source of the SHA-256 hashlock every leg shares (one 32-byte preimage unlocks BTC, the LP-90A0 swap precompile, and the EVM LXSwapHTLC.sol); keccak is explicitly excluded. - bitcoin.go — the fixed P2WSH HTLC script (OP_IF SHA256/EQUALVERIFY/CHECKSIG // OP_ELSE CLTV/DROP/CHECKSIG), P2WSHAddress, and claim/refund witnesses signed with real BIP143 segwit-v0 sighash via btcd txscript (no hand-rolled sighash; low-S RFC6979 sigs). - evm.go — lock/claim/refund calldata; selectors DERIVED from the canonical ABI signatures and asserted equal to the precompile's 0x4da2c728 / 0x84cc9dfb / 0x7249fbb6. Tests (-race) include real txscript.Engine execution proofs: claim spends with the correct preimage and fails with a wrong one; refund spends at/after locktime and fails before / with CLTV disabled. btcd pinned v0.24.2 (v0.26.0 split chaincfg/wire/txscript into /v2 modules and breaks the build).
53 lines
2.0 KiB
Go
53 lines
2.0 KiB
Go
// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
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// See the file LICENSE for licensing terms.
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// Package htlc constructs the three legs of a Lux cross-chain atomic swap from a
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// single shared primitive: a 32-byte Secret and its SHA-256 hashlock. The legs
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// are bound ONLY by that hashlock h = SHA256(s); one preimage s unlocks all of
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// them.
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//
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// - secret.go the chain-agnostic Secret + hashlock (THIS file): the one source
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// of the hashlock every leg shares.
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// - bitcoin.go the BTC P2WSH OP_SHA256/OP_CLTV HTLC script, address, and the
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// real BIP143 segwit-v0 claim/refund witnesses.
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// - evm.go lock/claim/refund calldata for the on-Lux swap precompile
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// (LP-90A0) and the LXSwapHTLC.sol counterparty contract.
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//
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// The hashlock is SHA-256 — matching Bitcoin's OP_SHA256 and the EVM 0x02
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// precompile, NEVER keccak — and the preimage is fixed at exactly 32 bytes so the
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// EVM bytes32 argument and the Bitcoin 32-byte witness push are the same value.
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package htlc
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import (
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"crypto/rand"
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"crypto/sha256"
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"crypto/subtle"
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"io"
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)
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// Secret is the 32-byte preimage s. Its SHA-256 hash is the hashlock h that every
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// leg of the swap is locked under; revealing s on any leg reveals it for all.
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type Secret [32]byte
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// NewSecret draws a uniform 32-byte secret from the OS CSPRNG.
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func NewSecret() (Secret, error) {
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var s Secret
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if _, err := io.ReadFull(rand.Reader, s[:]); err != nil {
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return Secret{}, err
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}
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return s, nil
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}
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// Hashlock is h = SHA256(s): the value the BTC script's OP_SHA256...OP_EQUALVERIFY
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// and the EVM legs' SHA-256 check all compare against.
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func (s Secret) Hashlock() [32]byte {
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return sha256.Sum256(s[:])
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}
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// VerifyPreimage reports whether SHA256(secret) == hashlock, in constant time.
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// This is the single check each leg performs on a revealed preimage.
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func VerifyPreimage(secret Secret, hashlock [32]byte) bool {
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got := sha256.Sum256(secret[:])
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return subtle.ConstantTimeCompare(got[:], hashlock[:]) == 1
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}
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