[9fans] encryption routines for il

[Russ Cox rsc@plan9.bell-labs.com]

Take Pace's il.tar.gz, make des.c a null file, and then
use the following encrypt.c:

(The inspiration and almost all of the code for this came from Kenji Arisawa.)

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#define DESKEYLEN 7
#define NAMELEN 22
typedef unsigned char uchar;

uchar a[8] = { 128, 64, 32, 16, 8, 4, 2, 1 };

/*  get bit status at the bit position n of string s
    char s[8]
    int n: 0 .. 63
*/
int strbit(char *s, int n)
{   int q,m;
    q = n / 8;
    m = n % 8;
    return (s[q] & a[m]?1:0);
}

/*  uchar s[8]
    uchar x[1]
    */
uchar s2b(uchar *s)
{   int i;
    uchar x;
    x = 0;
    for(i = 0; i < 8; i++) if(s[i]) x |= a[i];
    return x;
}

/*  uchar s[8]
    uchar x[1]
    */
void b2s(uchar x, uchar *s)
{   int i;
    for(i = 0; i < 8; i++) s[i] = 0;
    for(i = 0; i < 8; i++) if(x & a[i]) s[i] = 1;
}

/* uchar s[64], x[8] */
void blk2str(uchar *x, uchar *s)
{   int i;
    for(i = 0; i < 8; i++) b2s(x[i],&s[8*i]);
}

/* uchar s[64], x[8] */
void str2blk(uchar *s, uchar *x)
{   int i;
    for(i = 0; i < 8; i++) x[i] = s2b(&s[8*i]);
}

/* Plan9 encrypt
   uchar key[7]    --- deskey
   uchar t[8]     --- target(des cypher block)
 */
void des(uchar *key, uchar *t)
{   int i,j;
    char s[64],u[64];
    for(j = 0; j < 8; j++){
        for(i = 0; i < 7; i++) s[8*j + i] = strbit(key, 7*j + i);
        s[8*j + 7] = 0;
    }
    setkey(s);
    blk2str(t,u);
    encrypt(u,0); /* encrypt */
    str2blk(u,t);
}

void
plan9_encrypt(uchar *key, uchar *t, int len)
{
	des(key, t);
}

This doesn't work under Linux.  Don't complain to me.

Russ