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AES-CFB[18] 2x optimization. Well, I bet nobody cares about AES-CFB1

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performance, but anyway...
This commit is contained in:
Andy Polyakov 2004-12-30 10:43:33 +00:00
parent e90faddaf8
commit 2e4a99f38b
1 changed files with 21 additions and 47 deletions
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68
crypto/aes/aes_cfb.c
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@ -158,61 +158,35 @@ void AES_cfb128_encrypt(const unsigned char *in, unsigned char *out,
/* This expects a single block of size nbits for both in and out. Note that
it corrupts any extra bits in the last byte of out */
/* Untested, once it is working, it will be optimised */
void AES_cfbr_encrypt_block(const unsigned char *in,unsigned char *out,
const int nbits,const AES_KEY *key,
unsigned char *ivec,const int enc)
{
int n;
int n,rem,num;
unsigned char ovec[AES_BLOCK_SIZE*2];
assert(in && out && key && ivec);
if(enc)
{
if (nbits<=0 || nbits>128) return;
/* fill in the first half of the new IV with the current IV */
memcpy(ovec,ivec,AES_BLOCK_SIZE);
/* construct the new IV */
AES_encrypt(ivec,ovec,key);
/* encrypt the input */
for(n=0 ; n < (nbits+7)/8 ; ++n)
out[n]=in[n]^ovec[n];
/* fill in the first half of the new IV with the current IV */
memcpy(ovec,ivec,AES_BLOCK_SIZE);
/* and put the ciphertext in the second half */
memcpy(ovec+AES_BLOCK_SIZE,out,(nbits+7)/8);
/* shift ovec left most of the bits... */
memmove(ovec,ovec+nbits/8,AES_BLOCK_SIZE+(nbits%8 ? 1 : 0));
/* now the remaining bits */
if(nbits%8 != 0)
AES_encrypt(ivec,ivec,key);
num = (nbits+7)/8;
if (enc) /* encrypt the input */
for(n=0 ; n < num ; ++n)
out[n] = (ovec[AES_BLOCK_SIZE+n] = in[n] ^ ivec[n]);
else /* decrypt the input */
for(n=0 ; n < num ; ++n)
out[n] = (ovec[AES_BLOCK_SIZE+n] = in[n]) ^ ivec[n];
/* shift ovec left... */
rem = nbits%8;
num = nbits/8;
if(rem==0)
memcpy(ivec,ovec+num,AES_BLOCK_SIZE);
else
for(n=0 ; n < AES_BLOCK_SIZE ; ++n)
{
ovec[n]<<=nbits%8;
ovec[n]|=ovec[n+1]>>(8-nbits%8);
}
/* finally, move it back into place */
memcpy(ivec,ovec,AES_BLOCK_SIZE);
}
else
{
/* construct the new IV in the first half of ovec */
AES_encrypt(ivec,ovec,key);
/* decrypt the input */
for(n=0 ; n < (nbits+7)/8 ; ++n)
out[n]=in[n]^ovec[n];
/* fill in the first half of the new IV with the current IV */
memcpy(ovec,ivec,AES_BLOCK_SIZE);
/* append the ciphertext */
memcpy(ovec+AES_BLOCK_SIZE,in,(nbits+7)/8);
/* shift ovec left most of the bits... */
memmove(ovec,ovec+nbits/8,AES_BLOCK_SIZE+(nbits%8 ? 1 : 0));
/* now the remaining bits */
if(nbits%8 != 0)
for(n=0 ; n < AES_BLOCK_SIZE ; ++n)
{
ovec[n]<<=nbits%8;
ovec[n]|=ovec[n+1]>>(8-nbits%8);
}
/* finally, move it back into place */
memcpy(ivec,ovec,AES_BLOCK_SIZE);
}
ivec[n] = ovec[n+num]<<rem | ovec[n+num+1]>>(8-rem);
/* it is not necessary to cleanse ovec, since the IV is not secret */
}