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C nettle, low-level cryptographics library
C
C Copyright (C) 2013 Niels Möller
C
C The nettle library is free software; you can redistribute it and/or modify
C it under the terms of the GNU Lesser General Public License as published by
C the Free Software Foundation; either version 2.1 of the License, or (at your
C option) any later version.
C
C The nettle library is distributed in the hope that it will be useful, but
C WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
C or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
C License for more details.
C
C You should have received a copy of the GNU Lesser General Public License
C along with the nettle library; see the file COPYING.LIB. If not, write to
C the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
C MA 02111-1301, USA.
include_src(<arm/aes.m4>)
define(<PARAM_ROUNDS>, <r0>)
define(<PARAM_KEYS>, <r1>)
define(<TABLE>, <r2>)
define(<PARAM_LENGTH>, <r3>)
C On stack: DST, SRC
define(<W0>, <r4>)
define(<W1>, <r5>)
define(<W2>, <r6>)
define(<W3>, <r7>)
define(<T0>, <r8>)
define(<COUNT>, <r10>)
define(<KEY>, <r11>)
define(<MASK>, <r0>) C Overlaps inputs, except TABLE
define(<X0>, <r1>)
define(<X1>, <r3>)
define(<X2>, <r12>)
define(<X3>, <r14>) C lr
define(<FRAME_ROUNDS>, <[sp]>)
define(<FRAME_KEYS>, <[sp, #+4]>)
define(<FRAME_LENGTH>, <[sp, #+8]>)
C 8 saved registers
define(<FRAME_DST>, <[sp, #+44]>)
define(<FRAME_SRC>, <[sp, #+48]>)
define(<AES_DECRYPT_ROUND>, <
and T0, MASK, $1, lsl #2
ldr $5, [TABLE, T0]
and T0, MASK, $2, lsl #2
ldr $6, [TABLE, T0]
and T0, MASK, $3, lsl #2
ldr $7, [TABLE, T0]
and T0, MASK, $4, lsl #2
ldr $8, [TABLE, T0]
and T0, MASK, $4, ror #6
add TABLE, TABLE, #1024
ldr T0, [TABLE, T0]
eor $5, $5, T0
and T0, MASK, $1, ror #6
ldr T0, [TABLE, T0]
eor $6, $6, T0
and T0, MASK, $2, ror #6
ldr T0, [TABLE, T0]
eor $7, $7, T0
and T0, MASK, $3, ror #6
ldr T0, [TABLE, T0]
eor $8, $8, T0
and T0, MASK, $3, ror #14
add TABLE, TABLE, #1024
ldr T0, [TABLE, T0]
eor $5, $5, T0
and T0, MASK, $4, ror #14
ldr T0, [TABLE, T0]
eor $6, $6, T0
and T0, MASK, $1, ror #14
ldr T0, [TABLE, T0]
eor $7, $7, T0
and T0, MASK, $2, ror #14
ldr T0, [TABLE, T0]
eor $8, $8, T0
and T0, MASK, $2, ror #22
add TABLE, TABLE, #1024
ldr T0, [TABLE, T0]
eor $5, $5, T0
and T0, MASK, $3, ror #22
ldr T0, [TABLE, T0]
eor $6, $6, T0
and T0, MASK, $4, ror #22
ldr T0, [TABLE, T0]
eor $7, $7, T0
and T0, MASK, $1, ror #22
ldr T0, [TABLE, T0]
ldm $9!, {$1,$2,$3,$4}
eor $8, $8, T0
sub TABLE, TABLE, #3072
eor $5, $5, $1
eor $6, $6, $2
eor $7, $7, $3
eor $8, $8, $4
>)
.file "aes-decrypt-internal.asm"
C _aes_decrypt(unsigned rounds, const uint32_t *keys,
C const struct aes_table *T,
C size_t length, uint8_t *dst,
C uint8_t *src)
.text
ALIGN(4)
PROLOGUE(_nettle_aes_decrypt)
teq PARAM_LENGTH, #0
beq .Lend
push {r0,r1,r3, r4,r5,r6,r7,r8,r10,r11,lr}
mov MASK, #0x3fc
ALIGN(16)
.Lblock_loop:
ldr X0, FRAME_SRC C Use X0 as SRC pointer
ldm sp, {COUNT, KEY}
AES_LOAD(X0,KEY,W0)
AES_LOAD(X0,KEY,W1)
AES_LOAD(X0,KEY,W2)
AES_LOAD(X0,KEY,W3)
str X0, FRAME_SRC
add TABLE, TABLE, #AES_TABLE0
b .Lentry
ALIGN(16)
.Lround_loop:
C Transform X -> W
AES_DECRYPT_ROUND(X0, X1, X2, X3, W0, W1, W2, W3, KEY)
.Lentry:
subs COUNT, COUNT,#2
C Transform W -> X
AES_DECRYPT_ROUND(W0, W1, W2, W3, X0, X1, X2, X3, KEY)
bne .Lround_loop
lsr COUNT, MASK, #2 C Put the needed mask in the unused COUNT register
sub TABLE, TABLE, #AES_TABLE0
C Final round
AES_FINAL_ROUND_V5(X0, X3, X2, X1, KEY, W0, COUNT)
AES_FINAL_ROUND_V5(X1, X0, X3, X2, KEY, W1, COUNT)
AES_FINAL_ROUND_V5(X2, X1, X0, X3, KEY, W2, COUNT)
AES_FINAL_ROUND_V5(X3, X2, X1, X0, KEY, W3, COUNT)
ldr X0, FRAME_DST
ldr X1, FRAME_LENGTH
AES_STORE(X0,W0)
AES_STORE(X0,W1)
AES_STORE(X0,W2)
AES_STORE(X0,W3)
subs X1, X1, #16
str X0, FRAME_DST
str X1, FRAME_LENGTH
bhi .Lblock_loop
add sp, sp, #12 C Drop saved r0, r1, r3
pop {r4,r5,r6,r7,r8,r10,r11,pc}
.Lend:
bx lr
EPILOGUE(_nettle_aes_decrypt)
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