support SIGHASH_ANYONECANPAY in taproot sighash - #3
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Accept ALL | ANYONECANPAY (0x81, BIP341) in hashForTaprootSignature: skip the four all-input midstate hashes and commit to the signed input's outpoint, spent output and sequence instead. Write the full sighash type byte into the message (the masked byte was only correct for types without the flag) and fix the sign of the anyone-can-pay term in the buffer size formula. ANYONECANPAY alone (0x80) stays rejected: it is not a valid taproot sighash type. Golden values from btcd v0.24.2 with txscript.SigHashAll|txscript.SigHashAnyOneCanPay.
kovin-muun
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Jul 28, 2026
| * | ||
| * <p>Limitations: only SigHash.DEFAULT and SigHash.ALL without ANYONECANPAY are supported; SigHash.NONE, | ||
| * SigHash.SINGLE and the annex are not implemented. OP_CODESEPARATOR is not supported: the codesep_pos in the | ||
| * <p>Limitations: only SigHash.DEFAULT, SigHash.ALL and SigHash.ALL | SigHash.ANYONECANPAY are supported; |
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Why not just use the existing enum ANYONECANPAY_ALL?
This way you also don't need to loss the type Transaction.SigHash which was changed to byte in
Replace SigHash.ALL | SigHash.ANYONECANPAY with the existing ANYONECANPAY_ALL enum constant in javadoc, comments and tests. The test helper takes Transaction.SigHash again and converts with byteValue(), so call sites pass plain enum constants without casts. No behavior change.
kovin-muun
reviewed
Jul 28, 2026
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Accept ALL | ANYONECANPAY (0x81, BIP341) in hashForTaprootSignature: skip the four all-input midstate hashes and commit to the signed input's outpoint, spent output and sequence instead. Write the full sighash type byte into the message (the masked byte was only correct for types without the flag) and fix the sign of the anyone-can-pay term in the buffer size formula. ANYONECANPAY alone (0x80) stays rejected: it is not a valid taproot sighash type. Golden values from btcd v0.24.2 with txscript.SigHashAll|txscript.SigHashAnyOneCanPay.