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Poly1305 Aarch64 ASM: fix

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r^2 may overflow after adding high bits - reduce again.
This commit is contained in:
Sean Parkinson
2025-04-15 11:04:47 +10:00
parent b38ab8a064
commit 10f0999c21
1 changed files with 8 additions and 0 deletions
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8
wolfcrypt/src/port/arm/armv8-poly1305.c
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@ -931,6 +931,14 @@ int wc_Poly1305SetKey(Poly1305* ctx, const byte* key, word32 keySz)
"ADDS x8, x8, x14\n\t"
"ADCS x9, x9, x15\n\t"
"ADC x10, x10, xzr\n\t"
/* Get high bits from r^2[2]. */
"AND x11, x10, -4\n\t"
"AND x10, x10, 3\n\t"
"ADD x11, x11, x11, LSR 2\n\t"
/* Add top bits. */
"ADDS x8, x8, x11\n\t"
"ADCS x9, x9, xzr\n\t"
"ADC x10, x10, xzr\n\t"
/* 130-bits: Base 64 -> Base 26 */
"EXTR x15, x10, x9, #40\n\t"
"AND x14, x20, x9, LSR #14\n\t"