Re: [9fans] crypto question

["boyd, rounin" <boyd@insultant.net>]

>   I noticed that the libc function encrypt() uses some non-standard form 
> of cipher chaining.  In the normal case one byte from the previous block 

yeah that sounds right.

from:

    http://www.insultant.net/repo/des.msg

sed 's/.//' >9des.c <<'//GO.SYSIN DD 9des.c'
-/*
- *	Plan 9 DES encryption.
- */
-
-#include "des.h"
-
-int
-encrypt(void *key, void *data, int len)
-{
-	int	n;
-	int	r;
-	int	i;
-	char	*b;
-
-	if (len < DESBLOCKLEN)
-		return 0;
-
-	deskey(key);
-
-	len -= DESBLOCKLEN;
-	n = len / 7 + 1;
-	r = len % 7;
-
-	b = data;
-
-	for (i = 0; i < n; i++)
-	{
-		des(b, 0);
-		b += 7;
-	}
-
-	if (r)
-	{
-		b = data;
-		des(&b[len], 0);
-	}
-
-	return 1;
-}
-
-/*
- *	Plan 9 DES decryption.
- */
-int
-decrypt(void *key, void *data, int len)
-{
-	int	n;
-	int	r;
-	int	i;
-	char	*b;
-
-	if (len < DESBLOCKLEN)
-		return 0;
-
-	deskey(key);
-
-	len -= DESBLOCKLEN;
-	n = len / 7 + 1;
-	r = len % 7;
-
-	b = data;
-
-	if (r)
-		des(&b[len], 1);
-
-	b = &b[len - r];
-
-	for (i = 0; i < n; i++)
-	{
-		des(b, 1);
-		b -= 7;
-	}
-
-	return 1;
-}
-
-/*
- *	Convert a Plan 9 key to a DES key.
- */
-uchar	*
-des9key(uchar *key)
-{
-	int		i;
-	int		m1[]	= { 0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F };
-	int		m2[]	= { 0x00, 0xFC, 0xF8, 0xF0, 0xE0, 0xC0, 0x80 };
-	static uchar	nkey[DESKEYPLEN];
-
-	nkey[0] = key[0] & 0xFE;
-
-	for (i = 1; i < 7; i++)
-		nkey[i] = (key[i - 1] & m1[i]) << 8 - i | (key[i] & m2[i]) >> i;
-
-	nkey[7] = (key[6] & 0x7F) << 1;
-
-
-	return nkey;
-}
-
-/*
- *	Securenet challenge encryption.
- */
-int
-netcrypt(void *key, void *data)
-{
-	uchar	b[DESBLOCKLEN];
-
-	strncpy((char *)b, (char *)data, DESBLOCKLEN);
-
-	if (!encrypt(des9key(key), b, DESBLOCKLEN))
-		return 0;
-
-	sprint((char *)data, "%.2ux%.2ux%.2ux%.2ux", b[0], b[1], b[2], b[3]);
-	return 1;
-}
-
-/*
- *	Map a hexadecimal string to Securenet decimal string.
- */
-void
-sechex(char *buf)
-{
-	char	*p;
-
-	for (p = buf; *p != '\0'; p++)
-	{
-		switch (*p)
-		{
-		case 'A':
-		case 'B':
-		case 'C':
-		case 'a':
-		case 'b':
-		case 'c':
-			*p = '2';
-			break;
-
-		case 'D':
-		case 'E':
-		case 'F':
-		case 'd':
-		case 'e':
-		case 'f':
-			*p = '3';
-			break;
-		}
-	}
-}
//GO.SYSIN DD 9des.c

--
MGRS 31U DQ 52572 12604