cfb_enc.c

Netscape公司提供的安全套接字层

/* cfb_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_cfb_encrypt(in,out,numbits,length,schedule,ivec,encrypt)
unsigned char *in,*out;
int numbits;
long length;
des_key_schedule schedule;
des_cblock *ivec;
int encrypt;
    {
    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],to[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);
    if (encrypt)
        {
        while (l-- > 0)
            {
            ti[0]=v0;
            ti[1]=v1;
            des_encrypt((unsigned long *)ti,(unsigned long *)to,
                    schedule,DES_ENCRYPT);
            c2ln(in,d0,d1,n);
            in+=n;
            d0=(d0^to[0])&mask0;
            d1=(d1^to[1])&mask1;
            l2cn(d0,d1,out,n);
            out+=n;
            if (num > 32)
                {
                v0=((v1>>(num-32))|(d0<<(64-num)))&0xffffffff;
                v1=((d0>>(num-32))|(d1<<(64-num)))&0xffffffff;
                }
            else
                {
                v0=((v0>>num)|(v1<<(32-num)))&0xffffffff;
                v1=((v1>>num)|(d0<<(32-num)))&0xffffffff;
                }
            }
        }
    else
        {
        while (l-- > 0)
            {
            ti[0]=v0;
            ti[1]=v1;
            des_encrypt((unsigned long *)ti,(unsigned long *)to,
                    schedule,DES_ENCRYPT);
            c2ln(in,d0,d1,n);
            in+=n;
            if (num > 32)
                {
                v0=((v1>>(num-32))|(d0<<(64-num)))&0xffffffff;
                v1=((d0>>(num-32))|(d1<<(64-num)))&0xffffffff;
                }
            else
                {
                v0=((v0>>num)|(v1<<(32-num)))&0xffffffff;
                v1=((v1>>num)|(d0<<(32-num)))&0xffffffff;
                }
            d0=(d0^to[0])&mask0;
            d1=(d1^to[1])&mask1;
            l2cn(d0,d1,out,n);
            out+=n;
            }
        }
    iv=(unsigned char *)ivec;
    l2c(v0,iv);
    l2c(v1,iv);
    v0=v1=d0=d1=ti[0]=ti[1]=to[0]=to[1]=0;
    return(0);
    }