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SP ARM64 asm: fix Montgomery reduction by 4

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Handle add overflow properly in generic Montgomery reduction for 4
words. Used when reducing back to order of P-256 curve.
This commit is contained in:
Sean Parkinson
2023-11-07 11:39:03 +10:00
parent 2ee94023f9
commit 01c3345c7a
1 changed files with 6 additions and 0 deletions
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6
wolfcrypt/src/sp_arm64.c
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@ -40512,6 +40512,8 @@ static void sp_256_mont_mul_order_4(sp_digit* r, const sp_digit* a, const sp_dig
"adcs x11, x11, x3\n\t"
"umulh x4, x16, x17\n\t"
"adcs x12, x12, x4\n\t"
"# x15 == -1\n\t"
"adcs x19, x19, x15\n\t"
"csel x13, x13, xzr, cs\n\t"
"csel x14, x14, xzr, cs\n\t"
"csel x15, x15, xzr, cs\n\t"
@ -40703,6 +40705,8 @@ static void sp_256_mont_sqr_order_4(sp_digit* r, const sp_digit* a)
"adcs x10, x10, x2\n\t"
"umulh x3, x15, x16\n\t"
"adcs x11, x11, x3\n\t"
"# x14 == -1\n\t"
"adcs x17, x17, x14\n\t"
"csel x12, x12, xzr, cs\n\t"
"csel x13, x13, xzr, cs\n\t"
"csel x14, x14, xzr, cs\n\t"
@ -40889,6 +40893,8 @@ static void sp_256_mont_sqr_n_order_4(sp_digit* r, const sp_digit* a, int n)
"adcs x10, x10, x2\n\t"
"umulh x3, x15, x16\n\t"
"adcs x11, x11, x3\n\t"
"# x14 == -1\n\t"
"adcs x17, x17, x14\n\t"
"csel x12, x12, xzr, cs\n\t"
"csel x13, x13, xzr, cs\n\t"
"csel x14, x14, xzr, cs\n\t"