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Replace hardcoded values with compile-time hashing 

Previous changes enabled passing the string used as a tag into
`sha256t_hash_newtype!` macro rather than hard-coding midstate. This
commit takes advantage of it and replaces the hard-coded values with
compile-time executed (`const`) hashing.
This commit is contained in:
Martin Habovstiak 2023-04-02 15:53:43 +02:00
parent 095b7958dd
commit 91f45a214f
2 changed files with 4 additions and 40 deletions
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9
bitcoin/src/crypto/sighash.rs
View File

@ -33,13 +33,6 @@ pub(crate) const UINT256_ONE: [u8; 32] = [
0, 0, 0, 0, 0, 0, 0, 0
];
/// The SHA-256 midstate value for the [`TapSighash`].
pub(crate) const MIDSTATE_TAPSIGHASH: [u8; 32] = [
245, 4, 164, 37, 215, 248, 120, 59, 19, 99, 134, 138, 227, 229, 86, 88, 110, 238, 148, 93, 188,
120, 136, 221, 2, 166, 226, 195, 24, 115, 254, 159,
];
// f504a425d7f8783b1363868ae3e556586eee945dbc7888dd02a6e2c31873fe9f
macro_rules! impl_thirty_two_byte_hash {
($ty:ident) => {
impl secp256k1::ThirtyTwoByteHash for $ty {
@ -62,7 +55,7 @@ impl_thirty_two_byte_hash!(LegacySighash);
impl_thirty_two_byte_hash!(SegwitV0Sighash);
sha256t_hash_newtype! {
pub struct TapSighashTag = raw(MIDSTATE_TAPSIGHASH, 64);
pub struct TapSighashTag = hash_str("TapSighash");
/// Taproot-tagged hash with tag \"TapSighash\".
///

35
bitcoin/src/taproot.rs
View File

@ -21,30 +21,9 @@ pub use crate::crypto::taproot::{Error, Signature};
use crate::prelude::*;
use crate::{io, Script, ScriptBuf};
/// The SHA-256 midstate value for the TapLeaf hash.
const MIDSTATE_TAPLEAF: [u8; 32] = [
156, 224, 228, 230, 124, 17, 108, 57, 56, 179, 202, 242, 195, 15, 80, 137, 211, 243, 147, 108,
71, 99, 110, 96, 125, 179, 62, 234, 221, 198, 240, 201,
];
// 9ce0e4e67c116c3938b3caf2c30f5089d3f3936c47636e607db33eeaddc6f0c9
/// The SHA-256 midstate value for the TapBranch hash.
const MIDSTATE_TAPBRANCH: [u8; 32] = [
35, 168, 101, 169, 184, 164, 13, 167, 151, 124, 30, 4, 196, 158, 36, 111, 181, 190, 19, 118,
157, 36, 201, 183, 181, 131, 181, 212, 168, 210, 38, 210,
];
// 23a865a9b8a40da7977c1e04c49e246fb5be13769d24c9b7b583b5d4a8d226d2
/// The SHA-256 midstate value for the TapTweak hash.
const MIDSTATE_TAPTWEAK: [u8; 32] = [
209, 41, 162, 243, 112, 28, 101, 93, 101, 131, 182, 195, 185, 65, 151, 39, 149, 244, 226, 50,
148, 253, 84, 244, 162, 174, 141, 133, 71, 202, 89, 11,
];
// d129a2f3701c655d6583b6c3b941972795f4e23294fd54f4a2ae8d8547ca590b
// Taproot test vectors from BIP-341 state the hashes without any reversing
sha256t_hash_newtype! {
pub struct TapLeafTag = raw(MIDSTATE_TAPLEAF, 64);
pub struct TapLeafTag = hash_str("TapLeaf");
/// Taproot-tagged hash with tag \"TapLeaf\".
///
@ -52,7 +31,7 @@ sha256t_hash_newtype! {
#[hash_newtype(forward)]
pub struct TapLeafHash(_);
pub struct TapBranchTag = raw(MIDSTATE_TAPBRANCH, 64);
pub struct TapBranchTag = hash_str("TapBranch");
/// Tagged hash used in taproot trees.
///
@ -60,7 +39,7 @@ sha256t_hash_newtype! {
#[hash_newtype(forward)]
pub struct TapNodeHash(_);
pub struct TapTweakTag = raw(MIDSTATE_TAPTWEAK, 64);
pub struct TapTweakTag = hash_str("TapTweak");
/// Taproot-tagged hash with tag \"TapTweak\".
///
@ -1605,14 +1584,6 @@ mod test {
#[test]
fn test_midstates() {
use crate::crypto::sighash::MIDSTATE_TAPSIGHASH;
// check midstate against hard-coded values
assert_eq!(MIDSTATE_TAPLEAF, tag_engine("TapLeaf").midstate().to_byte_array());
assert_eq!(MIDSTATE_TAPBRANCH, tag_engine("TapBranch").midstate().to_byte_array());
assert_eq!(MIDSTATE_TAPTWEAK, tag_engine("TapTweak").midstate().to_byte_array());
assert_eq!(MIDSTATE_TAPSIGHASH, tag_engine("TapSighash").midstate().to_byte_array());
// test that engine creation roundtrips
assert_eq!(tag_engine("TapLeaf").midstate(), TapLeafTag::engine().midstate());
assert_eq!(tag_engine("TapBranch").midstate(), TapBranchTag::engine().midstate());