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