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/* ofb_enc.c */
/* Copyright (C) 1993 Eric Young - see README for more details */
/*-
* $Id: ofb_enc.c,v 1.2 1994/07/19 19:21:59 g89r4222 Exp $
*/
#include "des_locl.h"
/* The input and output are loaded in multiples of 8 bits.
* What this means is that if you hame numbits=12 and length=2
* the first 12 bits will be retrieved from the first byte and half
* the second. The second 12 bits will come from the 3rd and half the 4th
* byte.
*/
int des_ofb_encrypt(in,out,numbits,length,schedule,ivec)
unsigned char *in,*out;
int numbits;
long length;
des_key_schedule schedule;
des_cblock *ivec;
{
register unsigned long d0,d1,v0,v1,n=(numbits+7)/8;
register unsigned long mask0,mask1;
register long l=length;
register int num=numbits;
unsigned long ti[2];
unsigned char *iv;
if (num > 64) return(0);
if (num > 32)
{
mask0=0xffffffff;
if (num >= 64)
mask1=mask0;
else
mask1=(1L<<(num-32))-1;
}
else
{
if (num == 32)
mask0=0xffffffff;
else
mask0=(1L<<num)-1;
mask1=0x00000000;
}
iv=(unsigned char *)ivec;
c2l(iv,v0);
c2l(iv,v1);
ti[0]=v0;
ti[1]=v1;
while (l-- > 0)
{
des_encrypt((unsigned long *)ti,(unsigned long *)ti,
schedule,DES_ENCRYPT);
c2ln(in,d0,d1,n);
in+=n;
d0=(d0^ti[0])&mask0;
d1=(d1^ti[1])&mask1;
l2cn(d0,d1,out,n);
out+=n;
}
v0=ti[0];
v1=ti[1];
iv=(unsigned char *)ivec;
l2c(v0,iv);
l2c(v1,iv);
v0=v1=d0=d1=ti[0]=ti[1]=0;
return(0);
}
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