Commit 680fa880d63daa6058a084f1c107162e40e18aa8 | zig

author	Frank Denis <124872+jedisct1@users.noreply.github.com> 2021-07-22 01:27:42+02:00
committer	GitHub <noreply@github.com> 2021-07-22 01:27:42+02:00
log	680fa880d63daa6058a084f1c107162e40e18aa8
tree	b5f8ceee481384db3ed12e97ecf19bb49179c058
parent	8d0671157cdf8bc8b89d047138b42227420a5388
signature	Signed by PGP key 4AEE18F83AFDEB23

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];