improved precomputed value appending

AFK-AlignedFamKernel · Oct 10, 2024 · daa512d · daa512d
1 parent f882f6e
commit daa512d
Showing 1 changed file with 6 additions and 32 deletions.
diff --git a/onchain/cairo/src/bip340.cairo b/onchain/cairo/src/bip340.cairo
@@ -40,38 +40,12 @@ const p: u256 = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC
 /// `sha256(tag) || sha256(tag) || bytes(rx) || bytes(px) || m` as u256 where tag =
 /// "BIP0340/challenge".
 fn hash_challenge(rx: u256, px: u256, m: ByteArray) -> u256 {
-    // sha256(tag)
-    //Precomputed Values = compute_sha256_byte_array(@"BIP0340/challenge")
-    let (x0, x1, x2, x3, x4, x5, x6, x7) = (
-        2075471226,
-        2683263026,
-        1051836282,
-        1081979778,
-        3539202776,
-        464593487,
-        1241403791,
-        1833489276
-    );
-
-    let mut ba = Default::default();
-    // sha256(tag)
-    ba.append_word(x0.into(), 4);
-    ba.append_word(x1.into(), 4);
-    ba.append_word(x2.into(), 4);
-    ba.append_word(x3.into(), 4);
-    ba.append_word(x4.into(), 4);
-    ba.append_word(x5.into(), 4);
-    ba.append_word(x6.into(), 4);
-    ba.append_word(x7.into(), 4);
-    // sha256(tag)
-    ba.append_word(x0.into(), 4);
-    ba.append_word(x1.into(), 4);
-    ba.append_word(x2.into(), 4);
-    ba.append_word(x3.into(), 4);
-    ba.append_word(x4.into(), 4);
-    ba.append_word(x5.into(), 4);
-    ba.append_word(x6.into(), 4);
-    ba.append_word(x7.into(), 4);
+    //Precomputed values -> tag = 'compute_sha256_byte_array(@"BIP0340/challenge")'
+    // sha256(tag) || sha256(tag)
+    let mut ba: ByteArray = Default::default();
+    ba.append_word(0x7bb52d7a9fef58323eb1bf7a407db382d2f3f2d81bb1224f49fe518f6d48d3, 31);
+    ba.append_word(0x7c7bb52d7a9fef58323eb1bf7a407db382d2f3f2d81bb1224f49fe518f6d48, 31);
+    ba.append_word(0xd37c, 2);
     // bytes(rx)
     ba.append_word(rx.high.into(), 16);
     ba.append_word(rx.low.into(), 16);