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