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Date: Mon, 31 Mar 2008 09:35:54 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: passwords with fixed position characters and numbers

On Wed, Mar 26, 2008 at 10:11:43PM +0100, Ronald Brakeboer wrote:
> I only need some kind of script that generates all possible combinations
> from aaaa0000 - ZZZZ9999

Please find the brand new KnownForce external mode below, pre-configured
the way you have described above.

> And can someone tell me at what speed those could be generated in theory.

With this KnownForce mode and at these settings, I am getting over 1.5
million candidate passwords per second on a 1 GHz Pentium 3 running
Linux, with output to --stdout redirected to /dev/null.  When cracking
fast hashes (e.g., LM) with JtR itself, the c/s rate is even higher.

# Generic implementation of exhaustive search for a partially-known password.
# This is pre-configured for length 8, lowercase and uppercase letters in the
# first 4 positions (52 different characters), and digits in the remaining 4
# positions - however, the corresponding part of init() may be modified to use
# arbitrary character sets or even fixed characters for each position.
[List.External:KnownForce]
int last;		// Last character position, zero-based
int lastofs;		// Last character position offset into charset[]
int lastid;		// Current character index in the last position
int id[0x7f];		// Current character indices for other positions
int charset[0x7f00];	// Character sets, 0x100 elements for each position

void init()
{
	int length;
	int pos, ofs, i, c;

	length = 8;	// Password length to try

/* This defines the character sets for different character positions */
	pos = 0;
	while (pos < 4) {
		ofs = pos++ << 8;
		i = 0;
		c = 'a';
		while (c <= 'z')
			charset[ofs + i++] = c++;
		c = 'A';
		while (c <= 'Z')
			charset[ofs + i++] = c++;
		charset[ofs + i] = 0;
	}
	while (pos < length) {
		ofs = pos++ << 8;
		i = 0;
		c = '0';
		while (c <= '9')
			charset[ofs + i++] = c++;
		charset[ofs + i] = 0;
	}

	last = length - 1;
	pos = -1;
	while (++pos <= last)
		word[pos] = charset[id[pos] = pos << 8];
	lastid = (lastofs = last << 8) - 1;
	word[pos] = 0;
}

void generate()
{
	int pos;

/* Handle the typical case specially */
	if (word[last] = charset[++lastid]) return;

	word[pos = last] = charset[lastid = lastofs];
	while (pos--) {			// Have a preceding position?
		if (word[pos] = charset[++id[pos]]) return;
		word[pos] = charset[id[pos] = pos << 8];
	}

	word = 0;			// We're done
}

void restore()
{
	int i, c;

/* Calculate the current length and infer the character indices */
	last = 0;
	while (c = word[last]) {
		i = lastofs = last << 8;
		while (charset[i] != c && charset[i]) i++;
		if (!charset[i]) i = lastofs; // Not found
		id[last++] = i;
	}
	lastid = id[--last];
}

-- 
Alexander Peslyak <solar at openwall.com>
GPG key ID: 5B341F15  fp: B3FB 63F4 D7A3 BCCC 6F6E  FC55 A2FC 027C 5B34 1F15
http://www.openwall.com - bringing security into open computing environments

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