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internal/sm2ec: fix order asm inverse

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Sun Yimin 2024-08-19 14:48:19 +08:00 committed by GitHub
parent dd5b54f503
commit 1f2a93916b
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GPG Key ID: B5690EEEBB952194
1 changed files with 3 additions and 2 deletions
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5
internal/sm2ec/p256_asm_ord.go
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@ -33,6 +33,7 @@ func P256OrdInverse(k []byte) ([]byte, error) {
}
x := new(p256OrdElement)
p256OrdBigToLittle(x, (*[32]byte)(k))
p256OrdMul(x, x, RR)
// Inversion is implemented as exponentiation with exponent p − 2.
// The sequence of 41 multiplications and 253 squarings is derived from the
// following addition chain generated with github.com/mmcloughlin/addchain v0.4.0.
@ -65,7 +66,7 @@ func P256OrdInverse(k []byte) ([]byte, error) {
// i244 = ((i231 << 2 + _11) << 7 + _111111) << 2
// i262 = ((1 + i244) << 10 + _1001) << 5 + _111
// i277 = ((i262 << 5 + _111) << 4 + _101) << 4
// return ((_101 + i277) << 9 + _1001) << 5 + _11
// return ((_101 + i277) << 9 + _1001) << 5 + 1
//
var z = new(p256OrdElement)
var t0 = new(p256OrdElement)
@ -155,7 +156,7 @@ func P256OrdInverse(k []byte) ([]byte, error) {
p256OrdSqr(t1, t1, 9)
p256OrdMul(t0, t0, t1)
p256OrdSqr(t0, t0, 5)
p256OrdMul(z, z, t0)
p256OrdMul(z, x, t0)
return p256OrderFromMont(z), nil
}