From c03f5aed910702d6b1910789b360135d5a813056 Mon Sep 17 00:00:00 2001 From: Egor Tensin Date: Fri, 29 May 2015 21:17:06 +0300 Subject: aes256ecb.asm: better comments (as in aes192.asm) --- src/aes256ecb.asm | 259 +++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 188 insertions(+), 71 deletions(-) (limited to 'src') diff --git a/src/aes256ecb.asm b/src/aes256ecb.asm index f67f4bd..68430a1 100644 --- a/src/aes256ecb.asm +++ b/src/aes256ecb.asm @@ -37,83 +37,200 @@ inverse_key_schedule oword 15 dup(0) @raw_aes256ecb_encrypt@48 endp expand_keys_256ecb proc - lea edx, [key_schedule + 20h] - movdqa [key_schedule], xmm1 - movdqa [key_schedule + 10h], xmm2 - - aeskeygenassist xmm7, xmm2, 1h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 2h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 4h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 8h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 10h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 20h - pshufd xmm7, xmm7, 0FFh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 0 - pshufd xmm7, xmm7, 0AAh - call gen_round_key - - aeskeygenassist xmm7, xmm2, 40h - pshufd xmm7, xmm7, 0FFh - call gen_round_key + ; A "word" (in terms of the FIPS 187 standard) is a 32-bit block. + ; Words are denoted by `w[N]`. + ; + ; A key schedule is composed of 14 "regular" keys and a dumb key for + ; the "whitening" step. + ; It's stored in `key_schedule`. + ; + ; A key schedule is thus composed of 60 "words". + ; The FIPS standard includes an algorithm to calculate these words via + ; a simple loop: + ; + ; i = 8 + ; while i < 60: + ; temp = w[i - 1] + ; if i % 8 == 0: + ; temp = SubWord(RotWord(temp))^Rcon + ; elif i % 8 == 4: + ; temp = SubWord(temp) + ; w[i] = w[i - 8]^temp + ; i = i + 1 + ; + ; The loop above may be unrolled like this: + ; + ; w[8] = SubWord(RotWord(w[7]))^Rcon^w[0] + ; w[9] = w[8]^w[1] + ; = SubWord(RotWord(w[7]))^Rcon^w[1]^w[0] + ; w[10] = w[9]^w[2] + ; = SubWord(RotWord(w[7]))^Rcon^w[2]^w[1]^w[0] + ; w[11] = w[10]^w[3] + ; = SubWord(RotWord(w[7]))^Rcon^w[3]^w[2]^w[1]^w[0] + ; w[12] = SubWord(w[11])^w[4] + ; w[13] = w[12]^w[5] + ; = SubWord(w[11])^w[5]^w[4] + ; w[14] = w[13]^w[6] + ; = SubWord(w[11])^w[6]^w[5]^w[4] + ; w[15] = w[14]^w[7] + ; = SubWord(w[11])^w[7]^w[6]^w[5]^w[4] + ; w[16] = SubWord(RotWord(w[15]))^Rcon^w[8] + ; w[17] = w[16]^w[9] + ; = SubWord(RotWord(w[15]))^Rcon^w[9]^w[8] + ; w[18] = w[17]^w[10] + ; = SubWord(RotWord(w[15]))^Rcon^w[10]^w[9]^w[8] + ; w[19] = w[18]^w[11] + ; = SubWord(RotWord(w[15]))^Rcon^w[11]^w[10]^w[9]^w[8] + ; w[20] = SubWord(w[19])^w[12] + ; w[21] = w[20]^w[13] + ; = SubWord(w[19])^w[13]^w[12] + ; w[22] = w[21]^w[14] + ; = SubWord(w[19])^w[14]^w[13]^w[12] + ; w[23] = w[22]^w[15] + ; = SubWord(w[19])^w[15]^w[14]^w[13]^w[12] + ; + ; ... and so on. + ; + ; The Intel AES-NI instruction set facilitates calculating SubWord + ; and RotWord using `aeskeygenassist`, which is used in this routine. + ; + ; Preconditions: + ; * xmm2[127:96] == w[7], + ; * xmm2[95:64] == w[6], + ; * xmm2[63:32] == w[5], + ; * xmm2[31:0] == w[4], + ; * xmm1[127:96] == w[3], + ; * xmm1[95:64] == w[2], + ; * xmm1[63:32] == w[1], + ; * xmm1[31:0] == w[0]. + + movdqa [key_schedule], xmm1 ; sets w[0], w[1], w[2], w[3] + movdqa [key_schedule + 10h], xmm2 ; sets w[4], w[5], w[6], w[7] + + lea edx, [key_schedule + 20h] ; ecx = &w[8] + + aeskeygenassist xmm7, xmm2, 1h ; xmm7[127:96] = RotWord(SubWord(w[7]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[8], w[9], w[10], w[11] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[11]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[12], w[13], w[14], w[15] + + aeskeygenassist xmm7, xmm2, 2h ; xmm7[127:96] = RotWord(SubWord(w[15]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[16], w[17], w[18], w[19] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[19]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[20], w[21], w[22], w[23] + + aeskeygenassist xmm7, xmm2, 4h ; xmm7[127:96] = RotWord(SubWord(w[23]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[24], w[25], w[26], w[27] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[27]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[28], w[29], w[30], w[31] + + aeskeygenassist xmm7, xmm2, 8h ; xmm7[127:96] = RotWord(SubWord(w[31]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[32], w[33], w[34], w[35] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[35]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[36], w[37], w[38], w[39] + + aeskeygenassist xmm7, xmm2, 10h ; xmm7[127:96] = RotWord(SubWord(w[39]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[40], w[41], w[42], w[43] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[43]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[44], w[45], w[46], w[47] + + aeskeygenassist xmm7, xmm2, 20h ; xmm7[127:96] = RotWord(SubWord(w[47]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[48], w[49], w[50], w[51] + + aeskeygenassist xmm7, xmm2, 0 ; xmm7[95:64] = SubWord(w[51]) + pshufd xmm7, xmm7, 0AAh ; xmm7[127:96] = xmm7[63:32] = xmm7[31:0] = xmm7[95:64] + call gen_round_key ; sets w[52], w[53], w[54], w[55] + + aeskeygenassist xmm7, xmm2, 40h ; xmm7[127:96] = RotWord(SubWord(w[55]))^Rcon + pshufd xmm7, xmm7, 0FFh ; xmm7[95:64] = xmm7[63:32] = xmm7[31:0] = xmm7[127:96] + call gen_round_key ; sets w[56], w[57], w[58], w[59] call invert_key_schedule ret gen_round_key: - movdqa xmm6, xmm1 - - pslldq xmm6, 4 - pxor xmm1, xmm6 - pslldq xmm6, 4 - pxor xmm1, xmm6 - pslldq xmm6, 4 - pxor xmm1, xmm6 - - pxor xmm1, xmm7 - - movdqa [edx], xmm1 - add edx, 10h + ; Preconditions: + ; * xmm2[127:96] == w[i+7], + ; * xmm2[95:64] == w[i+6], + ; * xmm2[63:32] == w[i+5], + ; * xmm2[31:0] == w[i+4], + ; * xmm1[127:96] == w[i+3], + ; * xmm1[95:64] == w[i+2], + ; * xmm1[63:32] == w[i+1], + ; * xmm1[31:0] == w[i], + ; * xmm7[127:96] == xmm7[95:64] == xmm7[63:32] == xmm7[31:0] == HWGEN, + ; where HWGEN is either RotWord(SubWord(w[i+7]))^Rcon or SubWord(w[i+7]), + ; depending on the number of the round being processed, + ; * ecx == &w[i+8]. + ; + ; Postconditions: + ; * xmm2[127:96] == w[i+11] == HWGEN^w[i+3]^w[i+2]^w[i+1]^w[i], + ; * xmm2[95:64] == w[i+10] == HWGEN^w[i+2]^w[i+1]^w[i], + ; * xmm2[63:32] == w[i+9] == HWGEN^w[i+1]^w[i], + ; * xmm2[31:0] == w[i+8] == HWGEN^w[i], + ; * xmm1[127:96] == w[i+7], + ; * xmm1[95:64] == w[i+6], + ; * xmm1[63:32] == w[i+5], + ; * xmm1[31:0] == w[i+4], + ; * ecx == &w[i+12], + ; * the value in xmm6 is also modified. + + ; Calculate + ; w[i+3]^w[i+2]^w[i+1]^w[i], + ; w[i+2]^w[i+1]^w[i], + ; w[i+1]^w[i] and + ; w[i]. + movdqa xmm6, xmm1 ; xmm6 = xmm1 + pslldq xmm6, 4 ; xmm6 <<= 32 + pxor xmm1, xmm6 ; xmm1 ^= xmm6 + pslldq xmm6, 4 ; xmm6 <<= 32 + pxor xmm1, xmm6 ; xmm1 ^= xmm6 + pslldq xmm6, 4 ; xmm6 <<= 32 + pxor xmm1, xmm6 ; xmm1 ^= xmm6 + ; xmm1[127:96] == w[i+3]^w[i+2]^w[i+1]^w[i] + ; xmm1[95:64] == w[i+2]^w[i+1]^w[i] + ; xmm1[63:32] == w[i+1]^w[i] + ; xmm1[31:0] == w[i] + + ; Calculate + ; HWGEN^w[i+3]^w[i+2]^w[i+1]^w[i], + ; HWGEN^w[i+2]^w[i+1]^w[i], + ; HWGEN^w[i+1]^w[i] and + ; HWGEN^w[i]. + pxor xmm1, xmm7 ; xmm1 ^= xmm7 + ; xmm1[127:96] == w[i+11] == HWGEN^w[i+3]^w[i+2]^w[i+1]^w[i] + ; xmm1[95:64] == w[i+10] == HWGEN^w[i+2]^w[i+1]^w[i] + ; xmm1[63:32] == w[i+9] == HWGEN^w[i+1]^w[i] + ; xmm1[31:0] == w[i+8] == HWGEN^w[i] + + ; Set w[i+8], w[i+9], w[i+10] and w[i+11]. + movdqa [edx], xmm1 ; w[i+8] = HWGEN^w[i] + ; w[i+9] = HWGEN^w[i+1]^w[i] + ; w[i+10] = HWGEN^w[i+2]^w[i+1]^w[i] + ; w[i+11] = HWGEN^w[i+3]^w[i+2]^w[i+1]^w[i] + add edx, 10h ; ecx = &w[i+12] + + ; Swap the values in xmm1 and xmm2. + pxor xmm1, xmm2 + pxor xmm2, xmm1 + pxor xmm1, xmm2 - movdqa xmm7, xmm1 - movdqa xmm1, xmm2 - movdqa xmm2, xmm7 ret invert_key_schedule: -- cgit v1.2.3