www.pudn.com > sslref30.zip > ofb_enc.c

/* ofb_enc.c */ 
/* Copyright (C) 1993 Eric Young - see README for more details */ 
#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< 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); 
    }