+/* 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;
+ unsigned char ovec[AES_BLOCK_SIZE*2];
+
+ assert(in && out && key && ivec);
+ if(enc)
+ {
+ /* 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)
+ 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 */
+ }
+
+/* N.B. This expects the input to be packed, MS bit first */
+void AES_cfb1_encrypt(const unsigned char *in, unsigned char *out,
+ const unsigned long length, const AES_KEY *key,
+ unsigned char *ivec, int *num, const int enc)
+ {
+ unsigned int n;
+ unsigned char c[1],d[1];
+
+ assert(in && out && key && ivec && num);
+ assert(*num == 0);
+
+ memset(out,0,(length+7)/8);
+ for(n=0 ; n < length ; ++n)
+ {
+ c[0]=(in[n/8]&(1 << (7-n%8))) ? 0x80 : 0;
+ AES_cfbr_encrypt_block(c,d,1,key,ivec,enc);
+ out[n/8]=(out[n/8]&~(1 << (7-n%8)))|((d[0]&0x80) >> (n%8));
+ }
+ }
+
+void AES_cfb8_encrypt(const unsigned char *in, unsigned char *out,
+ const unsigned long length, const AES_KEY *key,
+ unsigned char *ivec, int *num, const int enc)
+ {
+ unsigned int n;
+
+ assert(in && out && key && ivec && num);
+ assert(*num == 0);
+
+ for(n=0 ; n < length ; ++n)
+ AES_cfbr_encrypt_block(&in[n],&out[n],8,key,ivec,enc);
+ }
+
projects / openssl.git / commitdiff