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; ---------------------------------------------------------------------------
; Copyright (c) 2002, Dr Brian Gladman <brg@gladman.me.uk>, Worcester, UK.
; All rights reserved.
;
; LICENSE TERMS
;
; The free distribution and use of this software in both source and binary
; form is allowed (with or without changes) provided that:
;
; 1. distributions of this source code include the above copyright
; notice, this list of conditions and the following disclaimer;
;
; 2. distributions in binary form include the above copyright
; notice, this list of conditions and the following disclaimer
; in the documentation and/or other associated materials;
;
; 3. the copyright holder's name is not used to endorse products
; built using this software without specific written permission.
;
; ALTERNATIVELY, provided that this notice is retained in full, this product
; may be distributed under the terms of the GNU General Public License (GPL),
; in which case the provisions of the GPL apply INSTEAD OF those given above.
;
; DISCLAIMER
;
; This software is provided 'as is' with no explicit or implied warranties
; in respect of its properties, including, but not limited to, correctness
; and/or fitness for purpose.
; ---------------------------------------------------------------------------
; Issue Date: 1/06/2003
; An AES implementation for Pentium processors using the NASM assembler (see
; <http://sourceforge.net/projects/nasm>).This version provides the standard
; AES block length (128 bits, 16 bytes) with the same interface as that used
; in my C implementation. The eax, ecx and edx registers and the artihmetic
; status flags are not preserved. The ebx, esi, edi, and ebp registers are
; preserved across calls. Only encryption and decryption are provided here,
; here, the key scheduling code being that in aeskey.c compiled with USE_ASM
; defined. This code uses the VC++ register saving conentions; if it is used
; with another compiler, its conventions for using and saving registers will
; need to be checked (and calling conventions). The NASM command line for
; the VC++ custom build step is:
;
; nasm -O2 -f win32 -o "$(TargetDir)\$(InputName).obj" "$(InputPath)"
section .text ; use32
; aes_rval aes_encrypt(const unsigned char in_blk[],
; unsigned char out_blk[], const aes_encrypt_ctx cx[1]);
; aes_rval aes_decrypt(const unsigned char in_blk[],
; unsigned char out_blk[], const aes_decrypt_ctx cx[1]);
;
; comment in/out the following lines to obtain the desired subroutines
%define ENCRYPTION ; define if encryption is needed
%define DECRYPTION ; define if decryption is needed
; The DLL interface must use the _stdcall convention in which the number
; of bytes of parameter space is added after an @ to the sutine's name.
; We must also remove our parameters from the stack before return (see
; the do_ret macro). Define AES_DLL for the Dynamic Link Library version.
;%define AES_DLL
tlen: equ 1024 ; length of each of 4 'xor' arrays (256 32-bit words)
; offsets to parameters with one register pushed onto stack
in_blk: equ 4 ; input byte array address parameter
out_blk:equ 8 ; output byte array address parameter
ctx: equ 12 ; AES context structure
stk_spc:equ 24 ; stack space
; register mapping for encrypt and decrypt subroutines
%define r0 eax
%define r1 ebx
%define r2 esi
%define r3 edi
%define r4 ecx
%define r5 edx
%define r6 ebp
%define eaxl al
%define eaxh ah
%define ebxl bl
%define ebxh bh
%define ecxl cl
%define ecxh ch
%define edxl dl
%define edxh dh
; These macros take a 32-bit word representing a column and use each
; of its 4 bytes to index a table of 256 32-bit words which are xored
; into each of the four output columns. The output values are in the
; registers %1, %2, %3 and %4 and the column input is in %5 with %6
; as a scratch register.
; Parameters:
; %1 out_state[0]
; %2 out_state[1]
; %3 out_state[2]
; %4 out_state[3]
; %5 input register for the round (destroyed)
; %6 scratch register for the round
; %7 key schedule address for round (in form r6 + offset)
%macro do_fcol 8 ; first column forward round
movzx %6,%5l
mov %1,[%8]
xor %1,[4*%6+%7]
movzx %6,%5h
shr %5,16
mov %2,[%8+12]
xor %2,[4*%6+%7+tlen]
movzx %6,%5l
mov %3,[%8+ 8]
xor %3,[4*%6+%7+2*tlen]
movzx %6,%5h
mov %5,%4 ; save an input register value
mov %4,[%8+ 4]
xor %4,[4*%6+%7+3*tlen]
%endmacro
%macro do_icol 8 ; first column for inverse round
movzx %6,%5l
mov %1,[%8]
xor %1,[4*%6+%7]
movzx %6,%5h
shr %5,16
mov %2,[%8+ 4]
xor %2,[4*%6+%7+tlen]
movzx %6,%5l
mov %3,[%8+ 8]
xor %3,[4*%6+%7+2*tlen]
movzx %6,%5h
mov %5,%4 ; save an input register value
mov %4,[%8+12]
xor %4,[4*%6+%7+3*tlen]
%endmacro
%macro do_col 7 ; other columns for forward and inverse rounds
movzx %6,%5l
xor %1,[4*%6+%7]
movzx %6,%5h
shr %5,16
xor %2,[4*%6+%7+tlen]
movzx %6,%5l
xor %3,[4*%6+%7+2*tlen]
movzx %6,%5h
xor %4,[4*%6+%7+3*tlen]
%endmacro
; These macros implement stack based local variables
%macro save 2
mov [esp+4*%1],%2
%endmacro
%macro restore 2
mov %1,[esp+4*%2]
%endmacro
; This macro performs a forward encryption cycle. It is entered with
; the first previous round column values in r0, r1, r2 and r3 and
; exits with the final values in the same registers.
%macro fwd_rnd 1-2 _t_fn ; normal forward rounds
mov r4,r0
save 0,r2
save 1,r3
; compute new column values
do_fcol r0,r3,r2,r1, r4,r5, %2, %1 ; r4 = input r0
do_col r1,r0,r3,r2, r4,r5, %2 ; r4 = input r1 (saved in fcol_f)
restore r4,0
do_col r2,r1,r0,r3, r4,r5, %2 ; r4 = input r2
restore r4,1
do_col r3,r2,r1,r0, r4,r5, %2 ; r4 = input r3
%endmacro
; This macro performs an inverse encryption cycle. It is entered with
; the first previous round column values in r0, r1, r2 and r3 and
; exits with the final values in the same registers.
%macro inv_rnd 1-2 _t_in ; normal inverse round
mov r4,r0
save 0,r1
save 1,r2
; compute new column values
do_icol r0,r1,r2,r3, r4,r5, %2, %1 ; r4 = r0
do_col r3,r0,r1,r2, r4,r5, %2 ; r4 = r3 (saved in icol_f)
restore r4,1
do_col r2,r3,r0,r1, r4,r5, %2 ; r4 = r2
restore r4,0
do_col r1,r2,r3,r0, r4,r5, %2 ; r4 = r1
%endmacro
; the DLL has to implement the _stdcall calling interface on return
; In this case we have to take our parameters (3 4-byte pointers)
; off the stack
%macro do_ret 0
%ifdef AES_DLL
ret 12
%else
ret
%endif
%endmacro
%macro do_name 1
%ifndef AES_DLL
global %1
%1:
%else
global %1@12
export %1@12
%1@12:
%endif
%endmacro
; AES Encryption Subroutine
%ifdef ENCRYPTION
extern _t_fn
extern _t_fl
do_name _aes_encrypt
sub esp,stk_spc
mov [esp+20],ebp
mov [esp+16],ebx
mov [esp+12],esi
mov [esp+ 8],edi
mov r4,[esp+in_blk+stk_spc] ; input pointer
mov r6,[esp+ctx+stk_spc] ; key pointer
; input four columns and xor in first round key
mov r0,[r4 ]
mov r1,[r4+ 4]
xor r0,[r6 ]
xor r1,[r6+ 4]
mov r2,[r4+ 8]
mov r3,[r4+12]
xor r2,[r6+ 8]
xor r3,[r6+12]
; determine the number of rounds
mov r4,[r6+4*45]
mov r5,[r6+4*52]
xor r4,[r6+4*53]
xor r4,r5
je .1
cmp r5,10
je .3
cmp r5,12
je .2
mov ebp,[esp+20]
mov ebx,[esp+16]
mov esi,[esp+12]
mov edi,[esp+ 8]
lea esp,[esp+stk_spc]
mov eax,-1
do_ret
.1: fwd_rnd r6+ 16 ; 14 rounds for 256-bit key
fwd_rnd r6+ 32
lea r6,[r6+32]
.2: fwd_rnd r6+ 16 ; 12 rounds for 192-bit key
fwd_rnd r6+ 32
lea r6,[r6+32]
.3: fwd_rnd r6+ 16 ; 10 rounds for 128-bit key
fwd_rnd r6+ 32
fwd_rnd r6+ 48
fwd_rnd r6+ 64
fwd_rnd r6+ 80
fwd_rnd r6+ 96
fwd_rnd r6+112
fwd_rnd r6+128
fwd_rnd r6+144
fwd_rnd r6+160, _t_fl ; last round uses a different table
; move final values to the output array
mov r6,[esp+out_blk+stk_spc]
mov [r6+12],r3
mov [r6+8],r2
mov [r6+4],r1
mov [r6],r0
mov ebp,[esp+20]
mov ebx,[esp+16]
mov esi,[esp+12]
mov edi,[esp+ 8]
lea esp,[esp+stk_spc]
xor eax,eax
do_ret
%endif
; AES Decryption Subroutine
%ifdef DECRYPTION
extern _t_in
extern _t_il
do_name _aes_decrypt
sub esp,stk_spc
mov [esp+20],ebp
mov [esp+16],ebx
mov [esp+12],esi
mov [esp+ 8],edi
mov r4,[esp+in_blk+stk_spc] ; input pointer
mov r6,[esp+ctx+stk_spc] ; context pointer
; input four columns
mov r0,[r4]
mov r1,[r4+4]
mov r2,[r4+8]
mov r3,[r4+12]
; determine the number of rounds
mov r5,[r6+4*52]
mov r4,[r6+4*45]
xor r4,[r6+4*53]
xor r4,r5
jne .1
mov r5,14
; xor in initial keys
.1: lea r4,[4*r5]
xor r0,[r6+4*r4 ]
xor r1,[r6+4*r4+ 4]
xor r2,[r6+4*r4+ 8]
xor r3,[r6+4*r4+12]
cmp r5,10
je .3
cmp r5,12
je .2
cmp r5,14
jne .4
inv_rnd r6+208 ; 14 rounds for 256-bit key
inv_rnd r6+192
.2: inv_rnd r6+176 ; 12 rounds for 192-bit key
inv_rnd r6+160
.3: inv_rnd r6+144 ; 10 rounds for 128-bit key
inv_rnd r6+128
inv_rnd r6+112
inv_rnd r6+ 96
inv_rnd r6+ 80
inv_rnd r6+ 64
inv_rnd r6+ 48
inv_rnd r6+ 32
inv_rnd r6+ 16
inv_rnd r6, _t_il ; last round uses a different table
; move final values to the output array.
mov r6,[esp+out_blk+stk_spc]
mov [r6+12],r3
mov [r6+8],r2
mov [r6+4],r1
mov [r6],r0
mov ebp,[esp+20]
mov ebx,[esp+16]
mov esi,[esp+12]
mov edi,[esp+ 8]
lea esp,[esp+stk_spc]
xor eax,eax
do_ret
.4: mov ebp,[esp+20]
mov ebx,[esp+16]
mov esi,[esp+12]
mov edi,[esp+ 8]
lea esp,[esp+stk_spc]
mov eax,-1
do_ret
%endif
end