snuffle.c (was Re: Reuter on Bernstein Ruling)

[Adam Back <aba@dcs.ex.ac.uk>]

snuffle and unsnuffle are only 64 lines each... so here they are.  You
need snefru also (snuffle for those not following is a construction to
convert a hash function into an encryption function ... Bernstein's
example is set up to use snefru ... a hash function).

Hash function seem be generally exportable, though they are several
constructs which allow you to convert a hash function into an
encryption function, so it's not too clear why they should be exempt.

Probably one reason is that hash functions are used to create and
check signatures, and signature checking and making code
(authentication only) also seems to be allowed for export.

I expect you could come up with some creative ways of using
authentication systems to provide encryption too.

We've already got an MD5 and SHA1 in perl, now all we need is a nice
small implementation (probably in perl) of the below which can be used
for a .sig :-)

So I guess you guys are now allowed to talk about snuffle
implementation and it's design... any comments/reposts etc?

Shall we reimplement it in perl?

Adam

== snuffle.c =================8<==============================
#include <stdio.h>
#include "snefru.h"

#define NMAX 10000

main(argc,argv)
int argc;
char *argv[];
{
 register int ch;
 static unsigned char x[NMAX];
 register unsigned char y = 0;
 static unsigned char h[NMAX];
 static unsigned char m[32];
 static unsigned char l[64];
 static unsigned char k[64];
 register int n = 64;
 register int i;
 register WORD32 *wm = &m[0];
 register WORD32 *wl = &l[0];
 register int level = 3;

 SetupHash512();

 for (i = 0;i < 64;i++)
   x[i] = k[i] = h[i] = 0;
   /* What matters is x[9...63], y, k[0...63], h[0...63]. */

 i = 0;
 while (((ch = getchar()) != EOF) && (ch != '\n'))
   if (i < 64)
     k[i++] = (unsigned char) ch;
   else if (i < 119)
     x[i++ - 55] = (unsigned char) ch;
 if (argv[1])
   for (i = 0;argv[1][i] && (i < 64);i++)
     h[i] = argv[1][i];

 while ((ch = getchar()) != EOF)
  {
   if (!(n & 31))
    {
     for (i = 0;i < 64;i++)
       l[i] = k[i] ^ h[n - 64 + i];
     Hash512(wm,wl,level,8);
    }

   x[n] = x[n - 24] + x[n - 55] + ((unsigned char) ch);
   h[n] = x[n] + m[n & 31];
   y += h[n];
   (void) putchar((char) y);

   n++;
   if (n == NMAX)
    {
     for (i = 0;i < 64;i++)
      {
       x[(n & 31) + i] = x[n - 64 + i];
       h[(n & 31) + i] = h[n - 64 + i];
      }
     n = (NMAX & 31) + 64;
    }
  }
}
==============================8<==============================

= unsnuffl.c =================8<==============================
#include <stdio.h>
#include "snefru.h"

#define NMAX 10000

main(argc,argv)
int argc;
char *argv[];
{
 register int ch;
 static unsigned char x[NMAX];
 register unsigned char y = 0;
 static unsigned char h[NMAX];
 static unsigned char m[32];
 static unsigned char l[64];
 static unsigned char k[64];
 register int n = 64;
 register int i;
 register WORD32 *wm = &m[0];
 register WORD32 *wl = &l[0];
 register int level = 3;

 SetupHash512();

 for (i = 0;i < 64;i++)
   x[i] = k[i] = h[i] = 0;
   /* What matters is x[9...63], y, k[0...63], h[0...63]. */

 i = 0;
 while (((ch = getchar()) != EOF) && (ch != '\n'))
   if (i < 64)
     k[i++] = (unsigned char) ch;
   else if (i < 119)
     x[i++ - 55] = (unsigned char) ch;
 if (argv[1])
   for (i = 0;argv[1][i] && (i < 64);i++)
     h[i] = argv[1][i];

 while ((ch = getchar()) != EOF)
  {
   if (!(n & 31))
    {
     for (i = 0;i < 64;i++)
       l[i] = k[i] ^ h[n - 64 + i];
     Hash512(wm,wl,level,8);
    }

   h[n] = ch - y;
   y = ch;
   x[n] = h[n] - m[n & 31];
   (void) putchar((char) (x[n] - x[n - 24] - x[n - 55]));

   n++;
   if (n == NMAX)
    {
     for (i = 0;i < 64;i++)
      {
       x[(n & 31) + i] = x[n - 64 + i];
       h[(n & 31) + i] = h[n - 64 + i];
      }
     n = (NMAX & 31) + 64;
    }
  }
}
==============================8<==============================