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; This Source Code Form is subject to the terms of the Mozilla Public
; License, v. 2.0. If a copy of the MPL was not distributed with this
; file, You can obtain one at http://mozilla.org/MPL/2.0/.
; ** ARCFOUR implementation optimized for AMD64.
; **
; ** The throughput achieved by this code is about 320 MBytes/sec, on
; ** a 1.8 GHz AMD Opteron (rev C0) processor.
.CODE
; extern void ARCFOUR(RC4Context *cx, unsigned long long inputLen,
; const unsigned char *input, unsigned char *output);
ARCFOUR PROC
push rbp
push rbx
push rsi
push rdi
mov rbp, rcx ; key = ARG(key)
mov rbx, rdx ; rbx = ARG(len)
mov rsi, r8 ; in = ARG(in)
mov rdi, r9 ; out = ARG(out)
mov rcx, [rbp] ; x = key->x
mov rdx, [rbp+8] ; y = key->y
add rbp, 16 ; d = key->data
inc rcx ; x++
and rcx, 0ffh ; x &= 0xff
lea rbx, [rbx+rsi-8] ; rbx = in+len-8
mov r9, rbx ; tmp = in+len-8
mov rax, [rbp+rcx*8] ; tx = d[x]
cmp rbx, rsi ; cmp in with in+len-8
jl Lend ; jump if (in+len-8 < in)
Lstart:
add rsi, 8 ; increment in
add rdi, 8 ; increment out
;
; generate the next 8 bytes of the rc4 stream into r8
;
mov r11, 8 ; byte counter
@@:
add dl, al ; y += tx
mov ebx, [rbp+rdx*8] ; ty = d[y]
mov [rbp+rcx*8], ebx ; d[x] = ty
add bl, al ; val = ty + tx
mov [rbp+rdx*8], eax ; d[y] = tx
inc cl ; x++ (NEXT ROUND)
mov eax, [rbp+rcx*8] ; tx = d[x] (NEXT ROUND)
mov r8b, [rbp+rbx*8] ; val = d[val]
dec r11b
ror r8, 8 ; (ror does not change ZF)
jnz @b
;
; xor 8 bytes
;
xor r8, [rsi-8]
cmp rsi, r9 ; cmp in+len-8 with in
mov [rdi-8], r8
jle Lstart
Lend:
add r9, 8 ; tmp = in+len
;
; handle the last bytes, one by one
;
@@:
cmp r9, rsi ; cmp in with in+len
jle Lfinished ; jump if (in+len <= in)
add dl, al ; y += tx
mov ebx, [rbp+rdx*8] ; ty = d[y]
mov [rbp+rcx*8], ebx ; d[x] = ty
add bl, al ; val = ty + tx
mov [rbp+rdx*8], eax ; d[y] = tx
inc cl ; x++ (NEXT ROUND)
mov eax, [rbp+rcx*8] ; tx = d[x] (NEXT ROUND)
mov r8b, [rbp+rbx*8] ; val = d[val]
xor r8b, [rsi] ; xor 1 byte
mov [rdi], r8b
inc rsi ; in++
inc rdi
jmp @b
Lfinished:
dec rcx ; x--
mov [rbp-8], dl ; key->y = y
mov [rbp-16], cl ; key->x = x
pop rdi
pop rsi
pop rbx
pop rbp
ret
ARCFOUR ENDP
END
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