Commit a052dd65 authored by Ben Laurie's avatar Ben Laurie
Browse files

Add untested CFB-r mode. Will be tested soon.

parent 5cc2658c

crypto/aes/aes.h

+3 −0
Original line number Diff line number Diff line
@@ -95,6 +95,9 @@ void AES_cbc_encrypt(const unsigned char *in, unsigned char *out, 
void AES_cfb128_encrypt(const unsigned char *in, unsigned char *out,

	const unsigned long length, const AES_KEY *key,

	unsigned char *ivec, int *num, const int enc);

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);

void AES_ofb128_encrypt(const unsigned char *in, unsigned char *out,

	const unsigned long length, const AES_KEY *key,

	unsigned char *ivec, int *num);

crypto/aes/aes_cfb.c

+57 −0
Original line number Diff line number Diff line
@@ -155,3 +155,60 @@ void AES_cfb128_encrypt(const unsigned char *in, unsigned char *out, 
	*num=n;

}



/* 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)

    {

    unsigned int n;

    unsigned char ovec[AES_BLOCK_SIZE*2];



    assert(in && out && key && ivec);

    if(enc)

	{

	/* construct the new IV in the second half of ovec */

	AES_encrypt(ivec,ovec+AES_BLOCK_SIZE,key);

	/* encrypt the input */

	for(n=0 ; n < (nbits+7)/8 ; ++n)

	    out[n]=in[n]^ovec[n+AES_BLOCK_SIZE];

	/* fill in the first half of the new IV with the current IV */

	memcpy(ovec,ivec,AES_BLOCK_SIZE);

	/* 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);

	}

    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);

	}

    /* it is not necessary to cleanse ovec, since the IV is not secret */

    }