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C nettle, low-level cryptographics library
C
C Copyright (C) 2004, 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., 59 Temple Place - Suite 330, Boston,
C MA 02111-1307, USA.
.file "arcfour-crypt.asm"
C arcfour_crypt(struct arcfour_ctx *ctx,
C unsigned length, uint8_t *dst,
C const uint8_t *src)
.text
ALIGN(4)
PROLOGUE(nettle_arcfour_crypt)
C save all registers that need to be saved
pushl %ebx C 12(%esp)
pushl %ebp C 8(%esp)
pushl %esi C 4(%esp)
pushl %edi C 0(%esp)
C Input arguments:
C ctx = 20(%esp)
C length = 24(%esp)
C dst = 28(%esp)
C src = 32(%esp)
C Register usage:
C %ebp = ctx
C %esi = src
C %edi = dst
C %edx = loop counter
C %eax = i
C %ebx = j
C %cl = si
C %ch = sj
movl 24(%esp), %edx C length
movl 20(%esp), %ebp C ctx
movl 28(%esp), %edi C dst
movl 32(%esp), %esi C src
lea (%edx, %edi), %edi
lea (%edx, %esi), %esi
negl %edx
jnc .Lend
movzbl ARCFOUR_I (%ebp), %eax C i
movzbl ARCFOUR_J (%ebp), %ebx C j
incb %al
sarl $1, %edx
jc .Lloop_odd
ALIGN(4)
.Lloop:
movb (%ebp, %eax), %cl C si.
addb %cl, %bl
movb (%ebp, %ebx), %ch C sj
movb %ch, (%ebp, %eax) C S[i] = sj
incl %eax
movzbl %al, %eax
movb %cl, (%ebp, %ebx) C S[j] = si
addb %ch, %cl
movzbl %cl, %ecx C Clear, so it can be used
C for indexing.
movb (%ebp, %ecx), %cl
xorb (%esi, %edx, 2), %cl
movb %cl, (%edi, %edx, 2)
C FIXME: Could exchange cl and ch in the second half
C and try to interleave instructions better.
.Lloop_odd:
movb (%ebp, %eax), %cl C si.
addb %cl, %bl
movb (%ebp, %ebx), %ch C sj
movb %ch, (%ebp, %eax) C S[i] = sj
incl %eax
movzbl %al, %eax
movb %cl, (%ebp, %ebx) C S[j] = si
addb %ch, %cl
movzbl %cl, %ecx C Clear, so it can be used
C for indexing.
movb (%ebp, %ecx), %cl
xorb 1(%esi, %edx, 2), %cl
incl %edx
movb %cl, -1(%edi, %edx, 2)
jnz .Lloop
C .Lloop_done:
decb %al
movb %al, ARCFOUR_I (%ebp) C Store the new i and j.
movb %bl, ARCFOUR_J (%ebp)
.Lend:
popl %edi
popl %esi
popl %ebp
popl %ebx
ret
EPILOGUE(nettle_arcfour_crypt)
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