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fix comments
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@maciejka
maciejka committed May 3, 2024
1 parent 2cc094e commit e5dcd9d
Showing 1 changed file with 36 additions and 13 deletions.
49 changes: 36 additions & 13 deletions onchain/src/bip340.cairo
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Original file line number Diff line number Diff line change
Expand Up @@ -26,11 +26,20 @@ const TWO_POW_96: u128 = 0x1000000000000000000000000;

const p: u256 = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F;

/// Computes BIP0340/challenge tagged hash.
///
/// # Parameters:
/// - `rx`: `u256` - The x-coordinate of the R point from the signature.
/// - `px`: `u256` - The x-coordinate of the public key.
/// - `m`: `ByteArray` - The message for which the signature is being verified.
///
/// # Returns:
/// Returns `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)
let [x0, x1, x2, x3, x4, x5, x6, x7] = compute_sha256_byte_array(@"BIP0340/challenge");

// sha256(tag) || sha256(tag) || bytes(r) || bytes(pk) || m
let mut ba = Default::default();
// sha256(tag)
ba.append_word(x0.into(), 4);
Expand All @@ -50,7 +59,7 @@ fn hash_challenge(rx: u256, px: u256, m: ByteArray) -> u256 {
ba.append_word(x5.into(), 4);
ba.append_word(x6.into(), 4);
ba.append_word(x7.into(), 4);
// bytes(r)
// bytes(rx)
ba.append_word(rx.high.into(), 16);
ba.append_word(rx.low.into(), 16);
// bytes(px)
Expand All @@ -67,6 +76,20 @@ fn hash_challenge(rx: u256, px: u256, m: ByteArray) -> u256 {
}
}

/// Verifies a signature according to the BIP-340.
///
/// This function checks if the signature `(rx, s)` is valid for a message `m` with
/// respect to the public key `px`.
///
/// # Parameters
/// - `px`: `u256` - The x-coordinate of the public key.
/// - `rx`: `u256` - The x-coordinate of the R point from the signature.
/// - `s`: `u256` - The scalar component of the signature.
/// - `m`: `ByteArray` - The message for which the signature is being verified.
///
/// # Returns
/// Returns `true` if the signature is valid for the given message and public key; otherwise,
/// returns `false`.
fn verify(px: u256, rx: u256, s: u256, m: ByteArray) -> bool {
let n = Secp256Trait::<Secp256k1Point>::get_curve_size();

Expand All @@ -83,7 +106,7 @@ fn verify(px: u256, rx: u256, s: u256, m: ByteArray) -> bool {
Option::None => { return false; }
};

// e = int(hashBIP0340/challenge(bytes(r) || bytes(P) || m)) mod n.
// e = int(hashBIP0340/challenge(bytes(rx) || bytes(px) || m)) mod n.
let e = hash_challenge(rx, px, m) % n;

let G = Secp256Trait::<Secp256k1Point>::get_generator_point();
Expand Down Expand Up @@ -126,7 +149,7 @@ mod tests {
let rx: u256 = 0xe907831f80848d1069a5371b402410364bdf1c5f8307b0084c55f1ce2dca8215;
let s: u256 = 0x25f66a4a85ea8b71e482a74f382d2ce5ebeee8fdb2172f477df4900d310536c0;
let m: u256 = 0x0;
assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}

#[test]
Expand All @@ -135,7 +158,7 @@ mod tests {
let rx: u256 = 0x6896bd60eeae296db48a229ff71dfe071bde413e6d43f917dc8dcf8c78de3341;
let s: u256 = 0x8906d11ac976abccb20b091292bff4ea897efcb639ea871cfa95f6de339e4b0a;
let m: u256 = 0x243f6a8885a308d313198a2e03707344a4093822299f31d0082efa98ec4e6c89;
assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}

#[test]
Expand All @@ -145,7 +168,7 @@ mod tests {
let s: u256 = 0xab745879a5ad954a72c45a91c3a51d3c7adea98d82f8481e0e1e03674a6f3fb7;
let m: u256 = 0x7e2d58d8b3bcdf1abadec7829054f90dda9805aab56c77333024b9d0a508b75c;

assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}

#[test]
Expand All @@ -155,7 +178,7 @@ mod tests {
let s: u256 = 0x97582b9cb13db3933705b32ba982af5af25fd78881ebb32771fc5922efc66ea3;
let m: u256 = 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff;

assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}

#[test]
Expand All @@ -165,7 +188,7 @@ mod tests {
let s: u256 = 0x76afb1548af603b3eb45c9f8207dee1060cb71c04e80f593060b07d28308d7f4;
let m: u256 = 0x4df3c3f68fcc83b27e9d42c90431a72499f17875c81a599b566c9889b9696703;

assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}

#[test]
Expand Down Expand Up @@ -282,7 +305,7 @@ mod tests {
let rx: u256 = 0x71535db165ecd9fbbc046e5ffaea61186bb6ad436732fccc25291a55895464cf;
let s: u256 = 0x6069ce26bf03466228f19a3a62db8a649f2d560fac652827d1af0574e427ab63;
let m = "";
assert_eq!(verify(px, rx, s, m), true);
assert!(verify(px, rx, s, m));
}

#[test]
Expand All @@ -292,7 +315,7 @@ mod tests {
let rx: u256 = 0x8a20a0afef64124649232e0693c583ab1b9934ae63b4c3511f3ae1134c6a303;
let s: u256 = 0xea3173bfea6683bd101fa5aa5dbc1996fe7cacfc5a577d33ec14564cec2bacbf;
let m = "\x11";
assert_eq!(verify(px, rx, s, m), true);
assert!(verify(px, rx, s, m));
}

#[test]
Expand All @@ -303,7 +326,7 @@ mod tests {
let s: u256 = 0xc4a482b77bf960f8681540e25b6771ece1e5a37fd80e5a51897c5566a97ea5a5;
let m = "\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11";

assert_eq!(verify(px, rx, s, m), true);
assert!(verify(px, rx, s, m));
}

#[test]
Expand All @@ -325,7 +348,7 @@ mod tests {
m.append_byte(0x99);
m.append_byte(0x99);

assert_eq!(verify(px, rx, s, m), true);
assert!(verify(px, rx, s, m));
}

#[test]
Expand All @@ -336,6 +359,6 @@ mod tests {
let s: u256 = 0x2591fff0a4ac15d3ed5d3f767e686e771ec456af2fb53ffba163e509e16b0eba;
let m: u256 = 0x2e5673c8b39f7a0d41219676661159c59a93644c06b81684718b8a0cd53f7f06;

assert_eq!(verify(px, rx, s, m.into()), true);
assert!(verify(px, rx, s, m.into()));
}
}

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