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  • aes-encrypt-internal.asm 3.75 KiB
    C -*- mode: asm; asm-comment-char: ?C; -*-  
    C nettle, low-level cryptographics library
    C 
    C Copyright (C) 2001, 2002, 2005 Rafael R. Sevilla, Niels Mller
    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.
    
    include_src(<x86/aes.m4>)
    
    C Register usage:
    
    C AES state
    define(<SA>,<%eax>)
    define(<SB>,<%ebx>)
    define(<SC>,<%ecx>)
    define(<SD>,<%edx>)
    
    C Primary use of these registers. They're also used temporarily for other things.
    define(<T>,<%ebp>)
    define(<TMP>,<%edi>)
    define(<KEY>,<%esi>)
    
    define(<FRAME_CTX>,	<28(%esp)>)
    define(<FRAME_TABLE>,	<32(%esp)>)
    define(<FRAME_LENGTH>,	<36(%esp)>)
    define(<FRAME_DST>,	<40(%esp)>)
    define(<FRAME_SRC>,	<44(%esp)>)
    
    define(<FRAME_KEY>,	<4(%esp)>)
    define(<FRAME_COUNT>,	<(%esp)>)
    
    C The aes state is kept in %eax, %ebx, %ecx and %edx
    C
    C %esi is used as temporary, to point to the input, and to the
    C subkeys, etc.
    C
    C %ebp is used as the round counter, and as a temporary in the final round.
    C
    C %edi is a temporary, often used as an accumulator.
    
    	.file "aes-encrypt-internal.asm"
    	
    	C _aes_encrypt(struct aes_context *ctx, 
    	C	       const struct aes_table *T,
    	C	       unsigned length, uint8_t *dst,
    	C	       uint8_t *src)
    	.text
    	ALIGN(4)
    PROLOGUE(_nettle_aes_encrypt)
    	C save all registers that need to be saved
    	pushl	%ebx		C  20(%esp)
    	pushl	%ebp		C  16(%esp)
    	pushl	%esi		C  12(%esp)
    	pushl	%edi		C  8(%esp)
    
    	subl	$8, %esp	C  loop counter and save area for the key pointer
    
    	movl	FRAME_LENGTH, %ebp
    	testl	%ebp,%ebp
    	jz	.Lend
    
    	shrl	$4, FRAME_LENGTH
    .Lblock_loop:
    	movl	FRAME_CTX,KEY	C  address of context struct ctx
    	C  get number of rounds to do from ctx struct	
    	
    	movl	FRAME_SRC,TMP	C  address of plaintext
    	AES_LOAD(SA, SB, SC, SD, TMP, KEY)
    	addl	$16, FRAME_SRC	C Increment src pointer
    	movl	FRAME_TABLE, T
    
    	C  get number of rounds to do from ctx struct	
    	movl	AES_NROUNDS (KEY),TMP
    	subl	$1,TMP
    
    	C Loop counter on stack
    	movl	TMP, FRAME_COUNT
    
    	addl	$16,KEY		C  point to next key
    	movl	KEY,FRAME_KEY
    	ALIGN(4)
    .Lround_loop:
    	AES_ROUND(T, SA,SB,SC,SD, TMP, KEY)
    	pushl	TMP
    
    	AES_ROUND(T, SB,SC,SD,SA, TMP, KEY)
    	pushl	TMP
    
    	AES_ROUND(T, SC,SD,SA,SB, TMP, KEY)
    	pushl	TMP
    
    	AES_ROUND(T, SD,SA,SB,SC, TMP, KEY)
    	
    	movl	TMP,SD
    	popl	SC
    	popl	SB
    	popl	SA
    	
    	movl	FRAME_KEY, KEY
    
    	xorl	(KEY),SA	C  add current session key to plaintext
    	xorl	4(KEY),SB
    	xorl	8(KEY),SC
    	xorl	12(KEY),SD
    	addl	$16,FRAME_KEY	C  point to next key
    	decl	FRAME_COUNT
    	jnz	.Lround_loop
    
    	C last round
    
    	AES_FINAL_ROUND(SA,SB,SC,SD, T, TMP, KEY)
    	pushl	TMP
    
    	AES_FINAL_ROUND(SB,SC,SD,SA, T, TMP, KEY)
    	pushl	TMP
    
    	AES_FINAL_ROUND(SC,SD,SA,SB, T, TMP, KEY)
    	pushl	TMP
    
    	AES_FINAL_ROUND(SD,SA,SB,SC, T, TMP, KEY)
    
    	movl	TMP,SD
    	popl	SC
    	popl	SB
    	popl	SA
    
    	C S-box substitution
    	mov	$3,TMP
    .Lsubst:
    	AES_SUBST_BYTE(SA,SB,SC,SD, T, KEY)
    
    	decl	TMP
    	jnz	.Lsubst
    
    	C Add last subkey, and store encrypted data
    	movl	FRAME_DST,TMP
    	movl	FRAME_KEY, KEY
    	AES_STORE(SA,SB,SC,SD, KEY, TMP)
    	
    	addl	$16, FRAME_DST		C Increment destination pointer
    	decl	FRAME_LENGTH		C Length
    
    	jnz	.Lblock_loop
    
    .Lend:
    	addl	$8, %esp
    	popl	%edi
    	popl	%esi
    	popl	%ebp
    	popl	%ebx
    	ret
    EPILOGUE(_nettle_aes_encrypt)