94 lines
2.1 KiB
C
94 lines
2.1 KiB
C
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/* qud_cksm.c */
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/* Copyright (C) 1993 Eric Young - see README for more details */
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/*-
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* $Id: qud_cksm.c,v 1.2 1994/07/19 19:22:02 g89r4222 Exp $
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*/
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/* From "Message Authentication" R.R. Jueneman, S.M. Matyas, C.H. Meyer
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* IEEE Communications Magazine Sept 1985 Vol. 23 No. 9 p 29-40
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* This module in only based on the code in this paper and is
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* almost definitely not the same as the MIT implementation.
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*/
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#include "des_locl.h"
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/* bug fix for dos - 7/6/91 - Larry hughes@logos.ucs.indiana.edu */
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#define B0(a) (((unsigned long)(a)))
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#define B1(a) (((unsigned long)(a))<<8)
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#define B2(a) (((unsigned long)(a))<<16)
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#define B3(a) (((unsigned long)(a))<<24)
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/* used to scramble things a bit */
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/* Got the value MIT uses via brute force :-) 2/10/90 eay */
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#define NOISE ((unsigned long)83653421)
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unsigned long des_quad_cksum(input,output,length,out_count,seed)
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des_cblock *input;
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des_cblock *output;
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long length;
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int out_count;
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des_cblock *seed;
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{
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unsigned long z0,z1,t0,t1;
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int i;
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long l=0;
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unsigned char *cp;
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unsigned char *lp;
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if (out_count < 1) out_count=1;
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lp=(unsigned char *)output;
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z0=B0((*seed)[0])|B1((*seed)[1])|B2((*seed)[2])|B3((*seed)[3]);
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z1=B0((*seed)[4])|B1((*seed)[5])|B2((*seed)[6])|B3((*seed)[7]);
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for (i=0; ((i<4)&&(i<out_count)); i++)
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{
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cp=(unsigned char *)input;
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l=length;
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while (l > 0)
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{
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if (l > 1)
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{
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t0= (unsigned long)(*(cp++));
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t0|=(unsigned long)B1(*(cp++));
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l--;
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}
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else
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t0= (unsigned long)(*(cp++));
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l--;
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/* add */
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t0+=z0;
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t0&=0xffffffff;
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t1=z1;
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/* square, well sort of square */
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z0=((((t0*t0)&0xffffffff)+((t1*t1)&0xffffffff))
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&0xffffffff)%0x7fffffff;
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z1=((t0*((t1+NOISE)&0xffffffff))&0xffffffff)%0x7fffffff;
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}
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if (lp != NULL)
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{
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/* I believe I finally have things worked out.
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* The MIT library assumes that the checksum
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* is one huge number and it is returned in a
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* host dependant byte order.
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*/
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static unsigned long l=1;
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static unsigned char *c=(unsigned char *)&l;
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if (c[0])
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{
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l2c(z0,lp);
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l2c(z1,lp);
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}
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else
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{
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lp=output[out_count-i-1];
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l2n(z1,lp);
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l2n(z0,lp);
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}
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}
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}
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return(z0);
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}
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