Commit b8a77f3d5931e0bf4f3c5544957dd36380367a43 | zig

author	Frank Denis <124872+jedisct1@users.noreply.github.com> 2021-07-22 01:27:42+02:00
committer	Andrew Kelley <andrew@ziglang.org> 2021-08-31 13:31:06-07:00
log	b8a77f3d5931e0bf4f3c5544957dd36380367a43
tree	0983b03954e8020379656b8d3201173b8d9f35f3
parent	d4e22e3eb668968fa30f25c382b97629902f0bf8

std.crypto: handle the top bit in 25519.field.fromBytes64() (#9435)

The only known use case for this is the hash-to-curve operation where the top bit is always cleared.

But the function is public, so let's make it work as one would expect in the general case.

Also fix the comment by the way.

1 files changed, 2 insertions(+), 2 deletions(-)

lib
- std
  - crypto
    25519
    field.zig

lib/std/crypto/25519/field.zig+2-2

...	...	@@ -93,7 +93,7 @@ pub const Fe = struct {
93	93	return s;
94	94	}
95	95
96		/// Map a 64-bit big endian string into a field element
	96	/// Map a 64 bytes big endian string into a field element
97	97	pub fn fromBytes64(s: [64]u8) Fe {
98	98	var fl: [32]u8 = undefined;
99	99	var gl: [32]u8 = undefined;
...	...	@@ -106,7 +106,7 @@ pub const Fe = struct {
106	106	gl[31] &= 0x7f;
107	107	var fe_f = fromBytes(fl);
108	108	const fe_g = fromBytes(gl);
109		fe_f.limbs[0] += (s[32] >> 7) * 19;
	109	fe_f.limbs[0] += (s[32] >> 7) * 19 + @as(u10, s[0] >> 7) * 722;
110	110	i = 0;
111	111	while (i < 5) : (i += 1) {
112	112	fe_f.limbs[i] += 38 * fe_g.limbs[i];