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// vaeskf1.vi vd, vs2, rnd
#include "zvk_ext_macros.h"
#include "zvkned_ext_macros.h"
require_vaeskf_vi_constraints;
// There is one round constant for each round number
// between 1 and 10. We index using 'round# -1'.
static constexpr uint8_t kRoundConstants[10] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
};
// For AES128, AES192, or AES256, keys (and state) are handled as
// 128b/16B values.
//
// The Zvkned spec calls for handling the vector as made of EGU32x4
// element groups (i.e., 4 uint32_t), and FIPS-197 AES specification
// describes the key expansion in terms of manipulations of 32 bit
// words, so using the EGU32x4 is natural.
//
VI_ZVK_VD_VS2_ZIMM5_EGU32x4_NOVM_LOOP(
{},
// The following statements will be executed before the first execution
// of the loop, and only if the loop is going to be entered.
// We cannot use a block ( { ... } ) since we want the 'round' variable
// declared and defined here here to be visible in the loop block.
// Only consider the bottom 4 bits of the immediate.
const reg_t zimm4 = zimm5 & 0xF;
// Normalize the round value to be in [2, 14] by toggling bit 3
// if outside the range (i.e., +8 or -8).
const reg_t round = ((1 <= zimm4) && (zimm4 <= 10)) ? zimm4 : (zimm4 ^ 0x8);
const uint32_t rcon = kRoundConstants[round - 1];,
// Per Element Group body.
{
// vaeskf1_vi produces key[i+1] in vd, it receives key[i] in vs2,
// i.e., 4x32b values (4 words).
//
// The logic is fairly similar between vaeskf1/vaeskf2, with the following
// differences:
// - in AES-128 (vaeskf1), we get both the 'temp' word and
// the "previous words" w0..w3 from key[i]/vs2.
// - in AES-256 (vaeskf2), we get 'temp' from key[i]/vs2, and
// the "previous words" w0..w3 from key[i-1]/vd.
// 'temp' is extracted from the last (most significant) word of key[i].
uint32_t temp = vs2[3];
temp = (temp >> 8) | (temp << 24); // Rotate right by 8
temp = (((uint32_t)AES_ENC_SBOX[(temp >> 24) & 0xFF] << 24) |
((uint32_t)AES_ENC_SBOX[(temp >> 16) & 0xFF] << 16) |
((uint32_t)AES_ENC_SBOX[(temp >> 8) & 0xFF] << 8) |
((uint32_t)AES_ENC_SBOX[(temp >> 0) & 0xFF] << 0));
temp = temp ^ rcon;
// "old" words are the w[i-Nk] of FIPS-197. They are extracted
// from vs2, which contains key[i] in AES-128 where Nk=4.
const uint32_t w0 = vs2[0] ^ temp;
const uint32_t w1 = vs2[1] ^ w0;
const uint32_t w2 = vs2[2] ^ w1;
const uint32_t w3 = vs2[3] ^ w2;
// Overwrite vd with k[i+1] from the new words.
SET_EGU32x4_LE(vd, w0, w1, w2, w3);
}
);
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