| author |  Frank Denis <124872+jedisct1@users.noreply.github.com> 2020-10-06 14:02:06+02:00 |
| committer |  Andrew Kelley <andrew@ziglang.org> 2020-10-06 19:48:26-04:00 |
| log | fb63a2cfaecb981010e0b9d656fd372dbb331888 |
| tree | b2485d4d7c47286785db204dfbfc396065ec150a |
| parent | dd4771a5d2815004a75a90895fe45addb3a015d1 |
std/crypto: faster (mod 2^255-19) square root computation
251 squarings, 250 multiplications -> 251 squarings, 11 multiplications1 files changed, 8 insertions(+), 6 deletions(-)
lib
std
crypto
25519
lib/std/crypto/25519/field.zig+8-6
| ... | ... | @@ -307,12 +307,14 @@ pub const Fe = struct { |
| 307 | 307 | } |
| 308 | 308 | |
| 309 | 309 | pub fn pow2523(a: Fe) Fe { |
| 310 | var c = a; | |
| 311 | var i: usize = 0; | |
| 312 | while (i < 249) : (i += 1) { | |
| 313 | c = c.sq().mul(a); | |
| 314 | } | |
| 315 | return c.sq().sq().mul(a); | |
| 310 | var t0 = a.mul(a.sq()); | |
| 311 | var t1 = t0.mul(t0.sqn(2)).sq().mul(a); | |
| 312 | t0 = t1.sqn(5).mul(t1); | |
| 313 | var t2 = t0.sqn(5).mul(t1); | |
| 314 | t1 = t2.sqn(15).mul(t2); | |
| 315 | t2 = t1.sqn(30).mul(t1); | |
| 316 | t1 = t2.sqn(60).mul(t2); | |
| 317 | return t1.sqn(120).mul(t1).sqn(10).mul(t0).sqn(2).mul(a); | |
| 316 | 318 | } |
| 317 | 319 | |
| 318 | 320 | pub fn abs(a: Fe) Fe { |