[PROPOSAL/PATCH 2] Fortuna PRNG in /dev/random

[Jean-Luc Cooke]

Team,

I have attempted to gather everyones comments into this re-write of my Fortuna
/dev/random patch.  I will summarize.

1.      Requires the Cryptographic API.

2.      Enable the Fortuna replacement to random.c in the Cryptographic Options menu
        of kernel config.

3.      As-is, it checks at compile time that AES and SHA256 are built-in modules.

4.      You can change this block cipher and message digest setting in the
        crypto/random-fortuna.c file.  /proc/sys/kernel/random/digest_algo
	and cipher_algo are now strings telling the users what algorithms are
	being used.

5.      Entropy estimation still exists in much the same way as in the Legacay
        random.c with the following exceptions:
  a.    /proc/sys/kernel/random/read_wakeup_thresholds lower limit was 8, it is now
        0 for those of us crazy enough to want to remove blocking.
  b.    /proc/sys/kernel/random/entropy_avail only increases when data is added to
        pool-0.  Pool-0 is the only 1 out of 32 Fortuna pools which is drawn from
        at every reseeding.  So we don't over-estimate the amount of entropy we
        consume, this change was done.
  c.    Since Fortuna resists consuming its entropy, it seemed inappropriate to debit
        1MB of entropy from the count when reading 1MB from /dev/urandom.  Now, every
        reseeding deducts min(cipherKeySize, hashDigestSize) from the entropy count.
        It should be noted that by doubling the blocksize from which you read
        /dev/urandom, you double the speed since you reduce the number of reseeds by
        a half.

6.      The input mixing and output generation functions now use Fortuna
  a.    32 independent feedback input mixing pools using a cryptographic hash from the
        CryptoAPI are feed event data in round robin.
  b.    A block cipher in CTR mode generates the output.
  c.    Every file system block read from /dev/{u}random causes Fortuna to reseed
  	the block cipher's key with the digest output from 1 or more of the input
	mixing pools.  Pool-0 is used every time, pool-j is used every 2^j times.
	
7.      Since Fortuna resists consuming its entropy, saving the 2048 byte random-seed
        should be changed to:  dd if=/dev/urandom of=$seedfile bs=256 count=8.  After
        2^3 = 8 block reads, pools 0, 1, 2, and 3 will certainly be used.  After
        2^4 = 16, pools up to number 4 will be used and so on.

8.      The difference in bzImage size is 7,268 bytes on my P4 laptop.  This is a
        compressed image.  My comparison was the 2.6.8.1 tarball with no kernel config
        changes vs. Enabling the cryptoapi, Fortuna, AES (i586 assembly) and SHA256.
	I have not yet done run-time memory consumption comparisons, but
	Fortuna is certainly heavier than Legacy.

9.      The difference in performance in /dev/random is roughly a 32x decrease in
        output rates due to the 32x decrease in entropy estimation (see 5.c)

10.     The difference in performance in /dev/urandom is 3x increase in output rates
        for a 512 byte block size.  A doubling in block size, doubles the performance.
        I produced 512,000,000 bytes of output with a 32k block size in less than 10
        seconds.  The legacy /dev/urandom by comparison accomplished the same thing in
        2.5 minutes.  The assembly version of AES for the i586 gets credit for this.

I tried to test the syn-cookie code but was unable to determine if it works.
Printk()s in the syn cookie generation function were never called even though I
echod 1 to the proc file.  If someone can tell me what Im going wrong, I'd love
to test this further.

I'd appreciate beta-testers on other platforms to provide feedback.

JLC
diff -X exclude -Nur linux-2.6.8.1/crypto/Kconfig linux-2.6.8.1-rand2/crypto/Kconfig
--- linux-2.6.8.1/crypto/Kconfig	2004-08-14 06:56:22.000000000 -0400
+++ linux-2.6.8.1-rand2/crypto/Kconfig	2004-09-28 23:30:04.000000000 -0400
@@ -9,6 +9,15 @@
 	help
 	  This option provides the core Cryptographic API.
 
+config CRYPTO_RANDOM_FORTUNA
+	bool "The Fortuna RNG"
+	help
+	  Replaces the legacy Linux RNG with one using the crypto API
+	  and Fortuna by Ferguson and Schneier.  Entropy estimation, and
+	  a throttled /dev/random remain.  Improvements include faster
+	  /dev/urandom output and event input mixing.
+	  Note: Requires AES and SHA256 to be built-in.
+
 config CRYPTO_HMAC
 	bool "HMAC support"
 	depends on CRYPTO
diff -X exclude -Nur linux-2.6.8.1/crypto/random-fortuna.c linux-2.6.8.1-rand2/crypto/random-fortuna.c
--- linux-2.6.8.1/crypto/random-fortuna.c	1969-12-31 19:00:00.000000000 -0500
+++ linux-2.6.8.1-rand2/crypto/random-fortuna.c	2004-09-29 10:44:19.829932384 -0400
@@ -0,0 +1,2027 @@
+/*
+ * random-fortuna.c -- A cryptographically strong random number generator
+ *			using Fortuna.
+ *
+ * Version 2.1.1, last modified 28-Sep-2004
+ * 
+ * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
+ * rights reserved.
+ * Copyright Jean-Luc Cooke, 2004.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ * 
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU General Public License, in which case the provisions of the GPL are
+ * required INSTEAD OF the above restrictions.  (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ * 
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
+ * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+ * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+/*
+ * Taken from random.c, updated by Jean-Luc Cooke <jlcooke@xxxxxxxxxxxxxx>
+ * (now, with legal B.S. out of the way.....) 
+ * 
+ * This routine gathers environmental noise from device drivers, etc.,
+ * and returns good random numbers, suitable for cryptographic use.
+ * Besides the obvious cryptographic uses, these numbers are also good
+ * for seeding TCP sequence numbers, and other places where it is
+ * desirable to have numbers which are not only random, but hard to
+ * predict by an attacker.
+ *
+ * Theory of operation
+ * ===================
+ * 
+ * Computers are very predictable devices.  Hence it is extremely hard
+ * to produce truly random numbers on a computer --- as opposed to
+ * pseudo-random numbers, which can easily generated by using a
+ * algorithm.  Unfortunately, it is very easy for attackers to guess
+ * the sequence of pseudo-random number generators, and for some
+ * applications this is not acceptable.  So instead, we must try to
+ * gather "environmental noise" from the computer's environment, which
+ * must be hard for outside attackers to observe, and use that to
+ * generate random numbers.  In a Unix environment, this is best done
+ * from inside the kernel.
+ * 
+ * Sources of randomness from the environment include inter-keyboard
+ * timings, inter-interrupt timings from some interrupts, and other
+ * events which are both (a) non-deterministic and (b) hard for an
+ * outside observer to measure.  Randomness from these sources are
+ * added to an "entropy pool", which is mixed.
+ * As random bytes are mixed into the entropy pool, the routines keep
+ * an *estimate* of how many bits of randomness have been stored into
+ * the random number generator's internal state.
+ * 
+ * Even if it is possible to analyze Fortuna in some clever way, as
+ * long as the amount of data returned from the generator is less than
+ * the inherent entropy we've estimated in the pool, the output data
+ * is totally unpredictable.  For this reason, the routine decreases
+ * its internal estimate of how many bits of "true randomness" are
+ * contained in the entropy pool as it outputs random numbers.
+ * 
+ * If this estimate goes to zero, the routine can still generate
+ * random numbers; however, an attacker may (at least in theory) be
+ * able to infer the future output of the generator from prior
+ * outputs.  This requires successful cryptanalysis of Fortuna, which is
+ * not believed to be feasible, but there is a remote possibility.
+ * Nonetheless, these numbers should be useful for the vast majority
+ * of purposes.
+ * 
+ * Exported interfaces ---- output
+ * ===============================
+ * 
+ * There are three exported interfaces; the first is one designed to
+ * be used from within the kernel:
+ *
+ * 	void get_random_bytes(void *buf, int nbytes);
+ *
+ * This interface will return the requested number of random bytes,
+ * and place it in the requested buffer.
+ * 
+ * The two other interfaces are two character devices /dev/random and
+ * /dev/urandom.  /dev/random is suitable for use when very high
+ * quality randomness is desired (for example, for key generation or
+ * one-time pads), as it will only return a maximum of the number of
+ * bits of randomness (as estimated by the random number generator)
+ * contained in the entropy pool.
+ * 
+ * The /dev/urandom device does not have this limit, and will return
+ * as many bytes as are requested.  As more and more random bytes are
+ * requested without giving time for the entropy pool to recharge,
+ * this will result in random numbers that are merely cryptographically
+ * strong.  For many applications, however, this is acceptable.
+ *
+ * Exported interfaces ---- input
+ * ==============================
+ * 
+ * The current exported interfaces for gathering environmental noise
+ * from the devices are:
+ * 
+ * 	void add_keyboard_randomness(unsigned char scancode);
+ * 	void add_mouse_randomness(__u32 mouse_data);
+ * 	void add_interrupt_randomness(int irq);
+ * 
+ * add_keyboard_randomness() uses the inter-keypress timing, as well as the
+ * scancode as random inputs into the "entropy pool".
+ * 
+ * add_mouse_randomness() uses the mouse interrupt timing, as well as
+ * the reported position of the mouse from the hardware.
+ *
+ * add_interrupt_randomness() uses the inter-interrupt timing as random
+ * inputs to the entropy pool.  Note that not all interrupts are good
+ * sources of randomness!  For example, the timer interrupts is not a
+ * good choice, because the periodicity of the interrupts is too
+ * regular, and hence predictable to an attacker.  Disk interrupts are
+ * a better measure, since the timing of the disk interrupts are more
+ * unpredictable.
+ * 
+ * All of these routines try to estimate how many bits of randomness a
+ * particular randomness source.  They do this by keeping track of the
+ * first and second order deltas of the event timings.
+ *
+ * Ensuring unpredictability at system startup
+ * ============================================
+ * 
+ * When any operating system starts up, it will go through a sequence
+ * of actions that are fairly predictable by an adversary, especially
+ * if the start-up does not involve interaction with a human operator.
+ * This reduces the actual number of bits of unpredictability in the
+ * entropy pool below the value in entropy_count.  In order to
+ * counteract this effect, it helps to carry information in the
+ * entropy pool across shut-downs and start-ups.  To do this, put the
+ * following lines an appropriate script which is run during the boot
+ * sequence: 
+ *
+ *	echo "Initializing random number generator..."
+ *	random_seed=/var/run/random-seed
+ *	# Carry a random seed from start-up to start-up
+ *	# Load and then save the whole entropy pool
+ *	if [ -f $random_seed ]; then
+ *		cat $random_seed >/dev/urandom
+ *	else
+ *		touch $random_seed
+ *	fi
+ *	chmod 600 $random_seed
+ *	dd if=/dev/urandom of=$random_seed count=8 bs=256
+ *
+ * and the following lines in an appropriate script which is run as
+ * the system is shutdown:
+ *
+ *	# Carry a random seed from shut-down to start-up
+ *	# Save the whole entropy pool
+ * 	# Fortuna resists using all of its pool matirial, so we need to
+ *      # draw 8 seperate times (count=8) to ensure we get the entropy
+ *	# from pool[0,1,2,3]'s entropy.  count=2048 pool[0 .. 10], etc.
+ *	echo "Saving random seed..."
+ *	random_seed=/var/run/random-seed
+ *	touch $random_seed
+ *	chmod 600 $random_seed
+ *	dd if=/dev/urandom of=$random_seed count=8 bs=256
+ *
+ * For example, on most modern systems using the System V init
+ * scripts, such code fragments would be found in
+ * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
+ * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
+ * 
+ * Effectively, these commands cause the contents of the entropy pool
+ * to be saved at shut-down time and reloaded into the entropy pool at
+ * start-up.  (The 'dd' in the addition to the bootup script is to
+ * make sure that /etc/random-seed is different for every start-up,
+ * even if the system crashes without executing rc.0.)  Even with
+ * complete knowledge of the start-up activities, predicting the state
+ * of the entropy pool requires knowledge of the previous history of
+ * the system.
+ *
+ * Configuring the /dev/random driver under Linux
+ * ==============================================
+ *
+ * The /dev/random driver under Linux uses minor numbers 8 and 9 of
+ * the /dev/mem major number (#1).  So if your system does not have
+ * /dev/random and /dev/urandom created already, they can be created
+ * by using the commands:
+ *
+ * 	mknod /dev/random c 1 8
+ * 	mknod /dev/urandom c 1 9
+ * 
+ * Acknowledgements:
+ * =================
+ *
+ * Ideas for constructing this random number generator were derived
+ * from Pretty Good Privacy's random number generator, and from private
+ * discussions with Phil Karn.  Colin Plumb provided a faster random
+ * number generator, which speed up the mixing function of the entropy
+ * pool, taken from PGPfone.  Dale Worley has also contributed many
+ * useful ideas and suggestions to improve this driver.
+ * 
+ * Any flaws in the design are solely my (jlcooke) responsibility, and
+ * should not be attributed to the Phil, Colin, or any of authors of PGP
+ * or the legacy random.c (Ted Ts'o).
+ * 
+ * Further background information on this topic may be obtained from
+ * RFC 1750, "Randomness Recommendations for Security", by Donald
+ * Eastlake, Steve Crocker, and Jeff Schiller.  And Chapter 10 of
+ * Practical Cryptography by Ferguson and Schneier.
+ */
+
+#include <linux/utsname.h>
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/string.h>
+#include <linux/fcntl.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/poll.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/workqueue.h>
+#include <linux/genhd.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/crypto.h>
+#include <../crypto/internal.h>
+
+#include <asm/scatterlist.h>
+#include <asm/processor.h>
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+#include <asm/io.h>
+
+
+/*
+ * Configuration information
+ */
+#define BATCH_ENTROPY_SIZE 256
+#define USE_SHA256
+#define USE_AES
+
+/*
+ * Compile-time checking for our desired message digest
+ */
+#if defined USE_SHA256
+	#if !CONFIG_CRYPTO_SHA256
+		#error SHA256 not a built-in module, Fortuna configured to use it.
+	#endif
+	#define RANDOM_DEFAULT_DIGEST_ALGO "sha256"
+#elif defined USE_WHIRLPOOL
+	#if !CONFIG_CRYPTO_WHIRLPOOL
+		#error WHIRLPOOL not a built-in module, Fortuna configured to use it.
+	#endif
+	#define RANDOM_DEFAULT_DIGEST_ALGO "whirlpool"
+#else
+	#error Desired message digest algorithm not found
+#endif
+
+/*
+ * Compile-time checking for our desired block cipher
+ */
+#if defined USE_AES
+	#if (!CONFIG_CRYPTO_AES  &&  !CONFIG_CRYPTO_AES_586)
+		#error AES not a built-in module, Fortuna configured to use it.
+	#endif
+	#define RANDOM_DEFAULT_CIPHER_ALGO "aes"
+#elif defined USE_TWOFISH
+	#if (!CONFIG_CRYPTO_TWOFISH  &&  !CONFIG_CRYPTO_TWOFISH_586)
+		#error TWOFISH not a built-in module, Fortuna configured to use it.
+	#endif
+	#define RANDOM_DEFAULT_CIPHER_ALGO "twofish"
+#else
+	#error Desired block cipher algorithm not found
+#endif /* USE_AES */
+
+#define DEFAULT_POOL_NUMBER 5 /* 2^{5} = 32 pools */
+#define DEFAULT_POOL_SIZE ( (1<<DEFAULT_POOL_NUMBER) * 256)
+/* largest block of random data to extract at a time when in blocking-mode */
+#define TMP_BUF_SIZE		512
+/* SHA512/WHIRLPOOL have 64bytes == 512 bits */
+#define RANDOM_MAX_DIGEST_SIZE	64
+/* AES256 has 16byte blocks == 128 bits */
+#define RANDOM_MAX_BLOCK_SIZE	16
+/* AES256 has 32byte keys == 256 bits */
+#define RANDOM_MAX_KEY_SIZE	32
+
+#if 0
+	#define DEBUG_PRINTK  printk
+#else
+	#define DEBUG_PRINTK  noop_printk
+#endif
+#if 0
+	#define STATS_PRINTK  printk
+#else
+	#define STATS_PRINTK  noop_printk
+#endif
+static inline void noop_printk(const char *a, ...) {}
+
+/*
+ * The minimum number of bits of entropy before we wake up a read on
+ * /dev/random.  We also wait for reseed_count>0 and we do a 
+ * random_reseed() once we do wake up.
+ */
+static int random_read_wakeup_thresh = 64;
+
+/*
+ * If the entropy count falls under this number of bits, then we
+ * should wake up processes which are selecting or polling on write
+ * access to /dev/random.
+ */
+static int random_write_wakeup_thresh = 128;
+
+/*
+ * When the input pool goes over trickle_thresh, start dropping most
+ * samples to avoid wasting CPU time and reduce lock contention.
+ */
+
+static int trickle_thresh = DEFAULT_POOL_SIZE * 7;
+
+static DEFINE_PER_CPU(int, trickle_count) = 0;
+
+#define POOLBYTES\
+	( (1<<random_state->pool_number) * random_state->digestsize )
+#define POOLBITS	( POOLBYTES * 8 )
+
+/*
+ * Linux 2.2 compatibility
+ */
+#ifndef DECLARE_WAITQUEUE
+#define DECLARE_WAITQUEUE(WAIT, PTR)	struct wait_queue WAIT = { PTR, NULL }
+#endif
+#ifndef DECLARE_WAIT_QUEUE_HEAD
+#define DECLARE_WAIT_QUEUE_HEAD(WAIT) struct wait_queue *WAIT
+#endif
+
+/*
+ * Static global variables
+ */
+static struct entropy_store *random_state; /* The default global store */
+static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+
+/*
+ * Forward procedure declarations
+ */
+#ifdef CONFIG_SYSCTL
+static void sysctl_init_random(struct entropy_store *random_state);
+#endif
+
+/*****************************************************************
+ *
+ * Utility functions, with some ASM defined functions for speed
+ * purposes
+ * 
+ *****************************************************************/
+
+/*
+ * More asm magic....
+ * 
+ * For entropy estimation, we need to do an integral base 2
+ * logarithm.  
+ *
+ * Note the "12bits" suffix - this is used for numbers between
+ * 0 and 4095 only.  This allows a few shortcuts.
+ */
+#if 0	/* Slow but clear version */
+static inline __u32 int_ln_12bits(__u32 word)
+{
+	__u32 nbits = 0;
+	
+	while (word >>= 1)
+		nbits++;
+	return nbits;
+}
+#else	/* Faster (more clever) version, courtesy Colin Plumb */
+static inline __u32 int_ln_12bits(__u32 word)
+{
+	/* Smear msbit right to make an n-bit mask */
+	word |= word >> 8;
+	word |= word >> 4;
+	word |= word >> 2;
+	word |= word >> 1;
+	/* Remove one bit to make this a logarithm */
+	word >>= 1;
+	/* Count the bits set in the word */
+	word -= (word >> 1) & 0x555;
+	word = (word & 0x333) + ((word >> 2) & 0x333);
+	word += (word >> 4);
+	word += (word >> 8);
+	return word & 15;
+}
+#endif
+
+#if 0
+#define DEBUG_ENT(fmt, arg...) printk(KERN_DEBUG "random: " fmt, ## arg)
+#else
+#define DEBUG_ENT(fmt, arg...) do {} while (0)
+#endif
+
+/**********************************************************************
+ *
+ * OS independent entropy store.   Here are the functions which handle
+ * storing entropy in an entropy pool.
+ * 
+ **********************************************************************/
+
+struct entropy_store {
+	const char *digestAlgo;
+	unsigned int  digestsize;
+	struct crypto_tfm *pools[1<<DEFAULT_POOL_NUMBER];
+	/* optional, handy for statistics */
+	unsigned int pools_bytes[1<<DEFAULT_POOL_NUMBER];
+
+	const char *cipherAlgo;
+	/* the key */
+	unsigned char key[RANDOM_MAX_DIGEST_SIZE];
+	unsigned int  keysize;
+	/* the CTR value */
+	unsigned char iv[16];
+	unsigned int  blocksize;
+	struct crypto_tfm *cipher;
+
+	/* 2^pool_number # of pools */
+	unsigned int  pool_number;
+	/* current pool to add into */
+	unsigned int  pool_index;
+	/* size of the first pool */
+	unsigned int  pool0_len;
+	/* number of time we have reset */
+	unsigned int  reseed_count;
+	/* digest used during random_reseed() */
+	struct crypto_tfm *reseedHash;
+	/* cipher used for network randomness */
+	struct crypto_tfm *networkCipher;
+	/* flag indicating if networkCipher has been seeded */
+	char networkCipher_ready;
+
+	/* read-write data: */
+	spinlock_t lock ____cacheline_aligned_in_smp;
+	int		entropy_count;
+};
+
+/*
+ * Initialize the entropy store.  The input argument is the size of
+ * the random pool.
+ *
+ * Returns an negative error if there is a problem.
+ */
+static int create_entropy_store(int poolnum, struct entropy_store **ret_bucket)
+{
+	struct  entropy_store   *r;
+	unsigned long pool_number;
+	int     keysize, i, j;
+
+	pool_number = poolnum;
+
+	r = kmalloc(sizeof(struct entropy_store), GFP_KERNEL);
+	if (!r) {
+		return -ENOMEM;
+	}
+
+	memset (r, 0, sizeof(struct entropy_store));
+	r->pool_number = pool_number;
+	r->digestAlgo = RANDOM_DEFAULT_DIGEST_ALGO;
+
+DEBUG_PRINTK("create_entropy_store() pools=%u index=%u\n",
+	1<<pool_number, r->pool_index);
+	for (i=0; i<(1<<pool_number); i++) {
+DEBUG_PRINTK("create_entropy_store() i=%i index=%u\n", i, r->pool_index);
+		r->pools[i] = crypto_alloc_tfm(r->digestAlgo, 0);
+		if (r->pools[i] == NULL) {
+			for (j=0; j<i; j++) {
+				if (r->pools[j] != NULL) {
+					kfree(r->pools[j]);
+				}
+			}
+			kfree(r);
+			return -ENOMEM;
+		}
+		crypto_digest_init( r->pools[i] );
+	}
+	r->lock = SPIN_LOCK_UNLOCKED;
+	*ret_bucket = r;
+
+	r->cipherAlgo = RANDOM_DEFAULT_CIPHER_ALGO;
+	if ((r->cipher=crypto_alloc_tfm(r->cipherAlgo, 0)) == NULL) {
+		return -ENOMEM;
+	}
+
+	/* If the HASH's output is greater then the cipher's keysize, truncate
+	 * to the cipher's keysize */
+	keysize = crypto_tfm_alg_max_keysize(r->cipher);
+	r->digestsize = crypto_tfm_alg_digestsize(r->pools[0]);
+	r->blocksize = crypto_tfm_alg_blocksize(r->cipher);
+
+	r->keysize = (keysize < r->digestsize) ? keysize : r->digestsize;
+DEBUG_PRINTK("create_RANDOM %u %u %u\n", keysize, r->digestsize, r->keysize);
+
+	if (crypto_cipher_setkey(r->cipher, r->key, r->keysize)) {
+		return -EINVAL;
+	}
+
+	/* digest used duing random-reseed() */
+	if ((r->reseedHash=crypto_alloc_tfm(r->digestAlgo, 0)) == NULL) {
+		return -ENOMEM;
+	}
+	/* cipher used for network randomness */
+	if ((r->networkCipher=crypto_alloc_tfm(r->cipherAlgo, 0)) == NULL) {
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/*
+ * This function adds a byte into the entropy "pool".  It does not
+ * update the entropy estimate.  The caller should call
+ * credit_entropy_store if this is appropriate.
+ */
+static void add_entropy_words(struct entropy_store *r, const __u32 *in,
+			      int nwords)
+{
+	unsigned long flags;
+	struct scatterlist sg[1];
+	static unsigned int totalBytes=0;
+
+	if (r == NULL) {
+		return;
+	}
+
+	spin_lock_irqsave(&r->lock, flags);
+
+	totalBytes += nwords * sizeof(__u32);
+	r->pools_bytes[r->pool_index] += nwords * sizeof(__u32);
+
+	sg[0].page = virt_to_page(in);
+	sg[0].offset = offset_in_page(in);
+	sg[0].length = nwords*sizeof(__u32);
+	crypto_digest_update(r->pools[r->pool_index], sg, 1);
+
+	if (r->pool_index == 0) {
+		r->pool0_len += nwords*sizeof(__u32);
+	}
+DEBUG_PRINTK("r->pool0_len = %u\n", r->pool0_len);
+
+	/* idx = (idx + 1) mod ( (2^N)-1 ) */
+	r->pool_index = (r->pool_index + 1) & ((1<<r->pool_number)-1);
+
+	spin_unlock_irqrestore(&r->lock, flags);
+DEBUG_PRINTK("0 add_entropy_words() nwords=%u pool[i].bytes=%u total=%u\n",
+	nwords, r->pools_bytes[r->pool_index], totalBytes);
+}
+
+/*
+ * Credit (or debit) the entropy store with n bits of entropy
+ */
+static void credit_entropy_store(struct entropy_store *r, int nbits)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&r->lock, flags);
+
+	if (r->entropy_count + nbits < 0) {
+		DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
+			  r->entropy_count, nbits);
+		r->entropy_count = 0;
+	} else if (r->entropy_count + nbits > POOLBITS) {
+		r->entropy_count = POOLBITS;
+	} else {
+		r->entropy_count += nbits;
+		if (nbits)
+			DEBUG_ENT("%04d : added %d bits\n",
+				  r->entropy_count,
+				  nbits);
+	}
+
+	spin_unlock_irqrestore(&r->lock, flags);
+}
+
+/**********************************************************************
+ *
+ * Entropy batch input management
+ *
+ * We batch entropy to be added to avoid increasing interrupt latency
+ *
+ **********************************************************************/
+
+struct sample {
+	__u32 data[2];
+	int credit;
+};
+
+static struct sample *batch_entropy_pool, *batch_entropy_copy;
+static int	batch_head, batch_tail;
+static spinlock_t batch_lock = SPIN_LOCK_UNLOCKED;
+
+static int	batch_max;
+static void batch_entropy_process(void *private_);
+static DECLARE_WORK(batch_work, batch_entropy_process, NULL);
+
+/* note: the size must be a power of 2 */
+static int __init batch_entropy_init(int size, struct entropy_store *r)
+{
+	batch_entropy_pool = kmalloc(size*sizeof(struct sample), GFP_KERNEL);
+	if (!batch_entropy_pool)
+		return -1;
+	batch_entropy_copy = kmalloc(size*sizeof(struct sample), GFP_KERNEL);
+	if (!batch_entropy_copy) {
+		kfree(batch_entropy_pool);
+		return -1;
+	}
+	batch_head = batch_tail = 0;
+	batch_work.data = r;
+	batch_max = size;
+	return 0;
+}
+
+/*
+ * Changes to the entropy data is put into a queue rather than being added to
+ * the entropy counts directly.  This is presumably to avoid doing heavy
+ * hashing calculations during an interrupt in add_timer_randomness().
+ * Instead, the entropy is only added to the pool by keventd.
+ */
+void batch_entropy_store(u32 a, u32 b, int num)
+{
+	int new;
+	unsigned long flags;
+
+	if (!batch_max)
+		return;
+
+	spin_lock_irqsave(&batch_lock, flags);
+
+	batch_entropy_pool[batch_head].data[0] = a;
+	batch_entropy_pool[batch_head].data[1] = b;
+	batch_entropy_pool[batch_head].credit = num;
+
+	if (((batch_head - batch_tail) & (batch_max-1)) >= (batch_max / 2)) {
+		/*
+		 * Schedule it for the next timer tick:
+		 */
+		schedule_delayed_work(&batch_work, 1);
+	}
+
+	new = (batch_head+1) & (batch_max-1);
+	if (new == batch_tail) {
+		DEBUG_ENT("batch entropy buffer full\n");
+	} else {
+		batch_head = new;
+	}
+
+	spin_unlock_irqrestore(&batch_lock, flags);
+}
+
+EXPORT_SYMBOL(batch_entropy_store);
+
+/*
+ * Flush out the accumulated entropy operations, adding entropy to the passed
+ * store (normally random_state).  If that store has enough entropy, alternate
+ * between randomizing the data of the primary and secondary stores.
+ */
+static void batch_entropy_process(void *private_)
+{
+	int max_entropy = POOLBITS;
+	unsigned head, tail;
+
+	/* Mixing into the pool is expensive, so copy over the batch
+	 * data and release the batch lock. The pool is at least half
+	 * full, so don't worry too much about copying only the used
+	 * part.
+	 */
+	spin_lock_irq(&batch_lock);
+
+	memcpy(batch_entropy_copy, batch_entropy_pool,
+	       batch_max*sizeof(struct sample));
+
+	head = batch_head;
+	tail = batch_tail;
+	batch_tail = batch_head;
+
+	spin_unlock_irq(&batch_lock);
+
+	while (head != tail) {
+		if (random_state->entropy_count >= max_entropy) {
+			max_entropy = POOLBITS;
+		}
+		/*
+		 * Only credit if we're feeding into pool[0]
+		 * Otherwise we'd be assuming entropy in pool[31] would be
+		 * usable when we read.  This is conservative, but it'll
+		 * not over-credit our entropy estimate for users of
+		 * /dev/random, /dev/urandom will not be effected.
+		 */
+		if (random_state->pool_index == 0) {
+			credit_entropy_store(random_state,
+				batch_entropy_copy[tail].credit);
+		}
+		add_entropy_words(random_state,
+			batch_entropy_copy[tail].data, 2);
+		tail = (tail+1) & (batch_max-1);
+	}
+	if (random_state->entropy_count >= random_read_wakeup_thresh
+		|| random_state->reseed_count != 0)
+		wake_up_interruptible(&random_read_wait);
+}
+
+/*********************************************************************
+ *
+ * Entropy input management
+ *
+ *********************************************************************/
+
+/* There is one of these per entropy source */
+struct timer_rand_state {
+	__u32		last_time;
+	__s32		last_delta,last_delta2;
+	int		dont_count_entropy:1;
+};
+
+static struct timer_rand_state keyboard_timer_state;
+static struct timer_rand_state mouse_timer_state;
+static struct timer_rand_state extract_timer_state;
+static struct timer_rand_state *irq_timer_state[NR_IRQS];
+
+/*
+ * This function adds entropy to the entropy "pool" by using timing
+ * delays.  It uses the timer_rand_state structure to make an estimate
+ * of how many bits of entropy this call has added to the pool.
+ *
+ * The number "num" is also added to the pool - it should somehow describe
+ * the type of event which just happened.  This is currently 0-255 for
+ * keyboard scan codes, and 256 upwards for interrupts.
+ * On the i386, this is assumed to be at most 16 bits, and the high bits
+ * are used for a high-resolution timer.
+ *
+ */
+static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
+{
+	__u32		time;
+	__s32		delta, delta2, delta3;
+	int		entropy = 0;
+
+	/* if over the trickle threshold, use only 1 in 4096 samples */
+	if ( random_state->entropy_count > trickle_thresh &&
+	     (__get_cpu_var(trickle_count)++ & 0xfff))
+		return;
+
+#if defined (__i386__) || defined (__x86_64__)
+	if (cpu_has_tsc) {
+		__u32 high;
+		rdtsc(time, high);
+		num ^= high;
+	} else {
+		time = jiffies;
+	}
+#elif defined (__sparc_v9__)
+	unsigned long tick = tick_ops->get_tick();
+
+	time = (unsigned int) tick;
+	num ^= (tick >> 32UL);
+#else
+	time = jiffies;
+#endif
+
+	/*
+	 * Calculate number of bits of randomness we probably added.
+	 * We take into account the first, second and third-order deltas
+	 * in order to make our estimate.
+	 */
+	if (!state->dont_count_entropy) {
+		delta = time - state->last_time;
+		state->last_time = time;
+
+		delta2 = delta - state->last_delta;
+		state->last_delta = delta;
+
+		delta3 = delta2 - state->last_delta2;
+		state->last_delta2 = delta2;
+
+		if (delta < 0)
+			delta = -delta;
+		if (delta2 < 0)
+			delta2 = -delta2;
+		if (delta3 < 0)
+			delta3 = -delta3;
+		if (delta > delta2)
+			delta = delta2;
+		if (delta > delta3)
+			delta = delta3;
+
+		/*
+		 * delta is now minimum absolute delta.
+		 * Round down by 1 bit on general principles,
+		 * and limit entropy entimate to 12 bits.
+		 */
+		delta >>= 1;
+		delta &= (1 << 12) - 1;
+
+		entropy = int_ln_12bits(delta);
+	}
+	batch_entropy_store(num, time, entropy);
+}
+
+void add_keyboard_randomness(unsigned char scancode)
+{
+	static unsigned char last_scancode;
+	/* ignore autorepeat (multiple key down w/o key up) */
+	if (scancode != last_scancode) {
+		last_scancode = scancode;
+		add_timer_randomness(&keyboard_timer_state, scancode);
+	}
+}
+
+EXPORT_SYMBOL(add_keyboard_randomness);
+
+void add_mouse_randomness(__u32 mouse_data)
+{
+	add_timer_randomness(&mouse_timer_state, mouse_data);
+}
+
+EXPORT_SYMBOL(add_mouse_randomness);
+
+void add_interrupt_randomness(int irq)
+{
+	if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
+		return;
+
+	add_timer_randomness(irq_timer_state[irq], 0x100+irq);
+}
+
+EXPORT_SYMBOL(add_interrupt_randomness);
+
+void add_disk_randomness(struct gendisk *disk)
+{
+	if (!disk || !disk->random)
+		return;
+	/* first major is 1, so we get >= 0x200 here */
+	add_timer_randomness(disk->random,
+				0x100+MKDEV(disk->major, disk->first_minor));
+}
+
+EXPORT_SYMBOL(add_disk_randomness);
+
+/*********************************************************************
+ *
+ * Entropy extraction routines
+ *
+ *********************************************************************/
+
+#define EXTRACT_ENTROPY_USER		1
+#define EXTRACT_ENTROPY_LIMIT		4
+
+static ssize_t extract_entropy(struct entropy_store *r, void * buf,
+			       size_t nbytes, int flags);
+
+static inline void increment_iv(unsigned char *iv, const unsigned int IVsize) {
+	switch (IVsize) {
+		case 8:
+			if (++((u32*)iv)[0])
+				++((u32*)iv)[1];
+		break;
+
+		case 16:
+			if (++((u32*)iv)[0])
+				if (++((u32*)iv)[1])
+					if (++((u32*)iv)[2])
+						++((u32*)iv)[3];
+		break;
+
+		default:
+			{
+			int i;
+			for (i=0; i<IVsize; i++)
+				if (++iv[i])
+					break;
+			}
+		break;
+	}
+}
+
+/*
+ * Fortuna's Reseed
+ * 
+ * Key' = hash(Key || hash(pool[a0]) || hash(pool[a1]) || ...)
+ * where {a0,a1,...} are facators of r->reseed_count+1 which are of the form
+ * 2^j, 0<=j.
+ * Prevents backtracking attacks and with event inputs, supports forward
+ * secrecy
+ */
+static void random_reseed(struct entropy_store *r, size_t nbytes, int flags) {
+	struct scatterlist sg[1];
+	unsigned int i, deduct;
+	unsigned char tmp[RANDOM_MAX_DIGEST_SIZE];
+	unsigned long cpuflags;
+ 
+	deduct = (r->keysize < r->digestsize) ? r->keysize : r->digestsize;
+
+	/* Hold lock while accounting */
+	spin_lock_irqsave(&r->lock, cpuflags);
+
+	DEBUG_ENT("%04d : trying to extract %d bits\n",
+		  random_state->entropy_count,
+		  deduct * 8);
+
+	/*
+	 * Don't extract more data than in the entropy in the pooling system
+	 */
+	if (flags & EXTRACT_ENTROPY_LIMIT && nbytes >= r->entropy_count / 8) {
+		nbytes = r->entropy_count / 8;
+	}
+
+	if (deduct*8 <= r->entropy_count) {
+		r->entropy_count -= deduct*8;
+	} else {
+		r->entropy_count = 0;
+	}
+
+	if (r->entropy_count < random_write_wakeup_thresh)
+		wake_up_interruptible(&random_write_wait);
+
+	DEBUG_ENT("%04d : debiting %d bits%s\n",
+		  random_state->entropy_count,
+		  deduct * 8,
+		  flags & EXTRACT_ENTROPY_LIMIT ? "" : " (unlimited)");
+
+	r->reseed_count++;
+	r->pool0_len = 0;
+
+	/* Entropy accounting done, release lock. */
+	spin_unlock_irqrestore(&r->lock, cpuflags);
+
+	DEBUG_PRINTK("random_reseed count=%u\n", r->reseed_count);
+
+	crypto_digest_init(r->reseedHash);
+
+	sg[0].page = virt_to_page(r->key);
+	sg[0].offset = offset_in_page(r->key);
+	sg[0].length = r->keysize;
+	crypto_digest_update(r->reseedHash, sg, 1);
+
+#define TESTBIT(VAL, N)\
+  ( ((VAL) >> (N)) & 1 )
+	for (i=0; i<(1<<r->pool_number); i++) {
+		/* using pool[i] if r->reseed_count is divisible by 2^i
+		 * since 2^0 == 1, we always use pool[0]
+		 */
+		if ( (i==0)  ||  TESTBIT(r->reseed_count,i)==0 ) {
+			crypto_digest_final(r->pools[i], tmp);
+
+			sg[0].page = virt_to_page(tmp);
+			sg[0].offset = offset_in_page(tmp);
+			sg[0].length = r->keysize;
+			crypto_digest_update(r->reseedHash, sg, 1);
+
+			crypto_digest_init(r->pools[i]);
+			/* Each pool carries its past state forward */
+			crypto_digest_update(r->pools[i], sg, 1);
+		} else {
+			/* pool j is only used once every 2^j times */
+			break;
+		}
+	}
+#undef TESTBIT
+
+	crypto_digest_final(r->reseedHash, r->key);
+	crypto_cipher_setkey(r->cipher, r->key, r->keysize);
+	increment_iv(r->iv, r->blocksize);
+}
+
+
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a buffer.  This function computes how many remaining
+ * bits of entropy are left in the pool, but it does not restrict the
+ * number of bytes that are actually obtained.  If the EXTRACT_ENTROPY_USER
+ * flag is given, then the buf pointer is assumed to be in user space.
+ */
+static ssize_t extract_entropy(struct entropy_store *r, void * buf,
+			       size_t nbytes, int flags)
+{
+	ssize_t ret, i, deduct;
+	__u32 tmp[RANDOM_MAX_BLOCK_SIZE];
+	struct scatterlist sgiv[1], sgtmp[1];
+
+	/* Redundant, but just in case... */
+	if (r->entropy_count > POOLBITS)
+		r->entropy_count = POOLBITS;
+
+	/*
+	 * The size of block you read from at a go is directly related to
+	 * the number of Fortuna-reseeds you perform. And thus, the amount
+	 * of entropy you draw from the pooling system.
+	 *
+	 * Reading from /dev/urandom, you can specify any block size,
+	 * the larger the less Fortuna-reseeds, the faster the output.
+	 *
+	 * Reading from /dev/random however, we limit this to the amount of
+	 * entropy to deduct from our estimate.  This estimate is most
+	 * naturally updated from inside Fortuna-reseed, so we limit our block
+	 * size here.
+	 *
+	 * At most, Fortuna will use e=min(r->digestsize, r->keysize) of
+	 * entropy to reseed.
+	 */
+	deduct = (r->keysize < r->digestsize) ? r->keysize : r->digestsize;
+	if (flags & EXTRACT_ENTROPY_LIMIT  &&  deduct < nbytes) {
+		nbytes = deduct;
+	}
+
+	random_reseed(r, nbytes, flags);
+
+	sgiv[0].page = virt_to_page(r->iv);
+	sgiv[0].offset = offset_in_page(r->iv);
+	sgiv[0].length = r->blocksize;
+	sgtmp[0].page = virt_to_page(tmp);
+	sgtmp[0].offset = offset_in_page(tmp);
+	sgtmp[0].length = r->blocksize;
+
+	ret = 0;
+	while (nbytes) {
+		/*
+		 * Check if we need to break out or reschedule....
+		 */
+		if ((flags & EXTRACT_ENTROPY_USER) && need_resched()) {
+			if (signal_pending(current)) {
+				if (ret == 0)
+					ret = -ERESTARTSYS;
+				break;
+			}
+
+			DEBUG_ENT("%04d : extract sleeping (%d bytes left)\n",
+				  random_state->entropy_count,
+				  nbytes);
+
+			schedule();
+
+			/*
+			 * when we wakeup, there will be more data in our
+			 * pooling system so we will reseed
+			 */
+			random_reseed(r, nbytes, flags);
+
+			DEBUG_ENT("%04d : extract woke up\n",
+				  random_state->entropy_count);
+		}
+
+		crypto_cipher_encrypt(r->cipher, sgtmp, sgiv, r->blocksize);
+		increment_iv(r->iv, r->blocksize);
+		
+		/* Copy data to destination buffer */
+		i = (nbytes < r->blocksize) ? nbytes : r->blocksize;
+		if (flags & EXTRACT_ENTROPY_USER) {
+			i -= copy_to_user(buf, (__u8 const *)tmp, i);
+			if (!i) {
+				ret = -EFAULT;
+				break;
+			}
+		} else
+			memcpy(buf, (__u8 const *)tmp, i);
+		nbytes -= i;
+		buf += i;
+		ret += i;
+	}
+
+	/* generate a new key */
+	/* take into account the possibility that keysize >= blocksize */
+	for (i=0; i+r->blocksize<=r->keysize; i+=r->blocksize) {
+		sgtmp[0].page = virt_to_page( r->key+i );
+		sgtmp[0].offset = offset_in_page( r->key+i );
+		sgtmp[0].length = r->blocksize;
+		crypto_cipher_encrypt(r->cipher, sgtmp, sgiv, 1);
+		increment_iv(r->iv, r->blocksize);
+	}
+	sgtmp[0].page = virt_to_page( r->key+i );
+	sgtmp[0].offset = offset_in_page( r->key+i );
+	sgtmp[0].length = r->blocksize-i;
+	crypto_cipher_encrypt(r->cipher, sgtmp, sgiv, 1);
+	increment_iv(r->iv, r->blocksize);
+
+	if (crypto_cipher_setkey(r->cipher, r->key, r->keysize)) {
+		return -EINVAL;
+	}
+
+	/* Wipe data just returned from memory */
+	memset(tmp, 0, sizeof(tmp));
+	
+	return ret;
+}
+
+/*
+ * This function is the exported kernel interface.  It returns some
+ * number of good random numbers, suitable for seeding TCP sequence
+ * numbers, etc.
+ */
+void get_random_bytes(void *buf, int nbytes)
+{
+	if (random_state)
+		extract_entropy(random_state, (char *) buf, nbytes, 0);
+	else
+		printk(KERN_NOTICE "get_random_bytes called before "
+				   "random driver initialization\n");
+}
+
+EXPORT_SYMBOL(get_random_bytes);
+
+/*********************************************************************
+ *
+ * Functions to interface with Linux
+ *
+ *********************************************************************/
+
+/*
+ * Initialize the random pool with standard stuff.
+ * This is not secure random data, but it can't hurt us and people scream
+ * when you try to remove it.
+ *
+ * NOTE: This is an OS-dependent function.
+ */
+static void init_std_data(struct entropy_store *r)
+{
+	struct timeval 	tv;
+	__u32		words[2];
+	char 		*p;
+	int		i;
+
+	do_gettimeofday(&tv);
+	words[0] = tv.tv_sec;
+	words[1] = tv.tv_usec;
+	add_entropy_words(r, words, 2);
+
+	/*
+	 *	This doesn't lock system.utsname. However, we are generating
+	 *	entropy so a race with a name set here is fine.
+	 */
+	p = (char *) &system_utsname;
+	for (i = sizeof(system_utsname) / sizeof(words); i; i--) {
+		memcpy(words, p, sizeof(words));
+		add_entropy_words(r, words, sizeof(words)/4);
+		p += sizeof(words);
+	}
+}
+
+static int __init rand_initialize(void)
+{
+	int i;
+
+	if (create_entropy_store(DEFAULT_POOL_NUMBER, &random_state))
+		goto err;
+	if (batch_entropy_init(BATCH_ENTROPY_SIZE, random_state))
+		goto err;
+	init_std_data(random_state);
+#ifdef CONFIG_SYSCTL
+	sysctl_init_random(random_state);
+#endif
+	for (i = 0; i < NR_IRQS; i++)
+		irq_timer_state[i] = NULL;
+	memset(&keyboard_timer_state, 0, sizeof(struct timer_rand_state));
+	memset(&mouse_timer_state, 0, sizeof(struct timer_rand_state));
+	memset(&extract_timer_state, 0, sizeof(struct timer_rand_state));
+	extract_timer_state.dont_count_entropy = 1;
+	return 0;
+err:
+	return -1;
+}
+module_init(rand_initialize);
+
+void rand_initialize_irq(int irq)
+{
+	struct timer_rand_state *state;
+	
+	if (irq >= NR_IRQS || irq_timer_state[irq])
+		return;
+
+	/*
+	 * If kmalloc returns null, we just won't use that entropy
+	 * source.
+	 */
+	state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
+	if (state) {
+		memset(state, 0, sizeof(struct timer_rand_state));
+		irq_timer_state[irq] = state;
+	}
+}
+ 
+void rand_initialize_disk(struct gendisk *disk)
+{
+	struct timer_rand_state *state;
+	
+	/*
+	 * If kmalloc returns null, we just won't use that entropy
+	 * source.
+	 */
+	state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
+	if (state) {
+		memset(state, 0, sizeof(struct timer_rand_state));
+		disk->random = state;
+	}
+}
+
+static ssize_t
+random_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
+{
+	DECLARE_WAITQUEUE(wait, current);
+	ssize_t	n, retval = 0, count = 0,
+		max_xfer_size;
+	
+	if (nbytes == 0)
+		return 0;
+
+	/*
+	 * only read out of extract_entropy() the minimum bits of pool
+	 * matirial we can deduce from the output if we could attack our
+	 * block cipher and message digest functions in Fortuna
+	 */
+	max_xfer_size = (random_state->digestsize < random_state->keysize)
+			? random_state->keysize
+			: random_state->digestsize;
+
+	while (nbytes > 0) {
+		n = nbytes;
+		if (n > max_xfer_size)
+			n = max_xfer_size;
+
+		DEBUG_ENT("%04d : reading %d bits, p: %d s: %d\n",
+			  random_state->entropy_count,
+			  n*8, random_state->entropy_count,
+			  random_state->entropy_count);
+
+		n = extract_entropy(random_state, buf, n,
+				    EXTRACT_ENTROPY_USER |
+				    EXTRACT_ENTROPY_LIMIT);
+
+		DEBUG_ENT("%04d : read got %d bits (%d needed, reseeds=%d)\n",
+			  random_state->entropy_count,
+			  random_state->reseed_count,
+			  n*8, (nbytes-n)*8);
+
+		if (n == 0) {
+			if (file->f_flags & O_NONBLOCK) {
+				retval = -EAGAIN;
+				break;
+			}
+			if (signal_pending(current)) {
+				retval = -ERESTARTSYS;
+				break;
+			}
+
+			DEBUG_ENT("%04d : sleeping?\n",
+				  random_state->entropy_count);
+
+			set_current_state(TASK_INTERRUPTIBLE);
+			add_wait_queue(&random_read_wait, &wait);
+
+			if (random_state->entropy_count / 8 == 0
+				||  random_state->reseed_count == 0)
+				schedule();
+
+			set_current_state(TASK_RUNNING);
+			remove_wait_queue(&random_read_wait, &wait);
+
+			DEBUG_ENT("%04d : waking up\n",
+				  random_state->entropy_count);
+
+			continue;
+		}
+
+		if (n < 0) {
+			retval = n;
+			break;
+		}
+		count += n;
+		buf += n;
+		nbytes -= n;
+		break;		/* This break makes the device work */
+				/* like a named pipe */
+	}
+
+	/*
+	 * If we gave the user some bytes, update the access time.
+	 */
+	if (count)
+		file_accessed(file);
+	
+	return (count ? count : retval);
+}
+
+static ssize_t
+urandom_read(struct file * file, char __user * buf,
+		      size_t nbytes, loff_t *ppos)
+{
+	/* Don't return anything untill we've reseeded at least once */
+	if (random_state->reseed_count == 0)
+		return 0;
+
+	return extract_entropy(random_state, buf, nbytes,
+			       EXTRACT_ENTROPY_USER);
+}
+
+static unsigned int
+random_poll(struct file *file, poll_table * wait)
+{
+	unsigned int mask;
+
+	poll_wait(file, &random_read_wait, wait);
+	poll_wait(file, &random_write_wait, wait);
+	mask = 0;
+	if (random_state->entropy_count >= random_read_wakeup_thresh)
+		mask |= POLLIN | POLLRDNORM;
+	if (random_state->entropy_count < random_write_wakeup_thresh)
+		mask |= POLLOUT | POLLWRNORM;
+	return mask;
+}
+
+static ssize_t
+random_write(struct file * file, const char __user * buffer,
+	     size_t count, loff_t *ppos)
+{
+	int		ret = 0;
+	size_t		bytes;
+	__u32 		buf[16];
+	const char 	__user *p = buffer;
+	size_t		c = count;
+
+	while (c > 0) {
+		bytes = min(c, sizeof(buf));
+
+		bytes -= copy_from_user(&buf, p, bytes);
+		if (!bytes) {
+			ret = -EFAULT;
+			break;
+		}
+		c -= bytes;
+		p += bytes;
+
+		add_entropy_words(random_state, buf, (bytes + 3) / 4);
+	}
+	if (p == buffer) {
+		return (ssize_t)ret;
+	} else {
+		file->f_dentry->d_inode->i_mtime = CURRENT_TIME;
+		mark_inode_dirty(file->f_dentry->d_inode);
+		return (ssize_t)(p - buffer);
+	}
+}
+
+static int
+random_ioctl(struct inode * inode, struct file * file,
+	     unsigned int cmd, unsigned long arg)
+{
+	int size, ent_count;
+	int __user *p = (int __user *)arg;
+	int retval;
+	
+	switch (cmd) {
+	case RNDGETENTCNT:
+		ent_count = random_state->entropy_count;
+		if (put_user(ent_count, p))
+			return -EFAULT;
+		return 0;
+	case RNDADDTOENTCNT:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		if (get_user(ent_count, p))
+			return -EFAULT;
+		credit_entropy_store(random_state, ent_count);
+		/*
+		 * Wake up waiting processes if we have enough
+		 * entropy.
+		 */
+		if (random_state->entropy_count >= random_read_wakeup_thresh
+			&&  random_state->reseed_count != 0)
+			wake_up_interruptible(&random_read_wait);
+		return 0;
+	case RNDGETPOOL:
+		/* can't do this anymore */
+		return 0;
+	case RNDADDENTROPY:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		if (get_user(ent_count, p++))
+			return -EFAULT;
+		if (ent_count < 0)
+			return -EINVAL;
+		if (get_user(size, p++))
+			return -EFAULT;
+		retval = random_write(file, (const char __user *) p,
+				      size, &file->f_pos);
+		if (retval < 0)
+			return retval;
+		credit_entropy_store(random_state, ent_count);
+		/*
+		 * Wake up waiting processes if we have enough
+		 * entropy.
+		 */
+		if (random_state->entropy_count >= random_read_wakeup_thresh
+			&&  random_state->reseed_count != 0)
+			wake_up_interruptible(&random_read_wait);
+		return 0;
+	case RNDZAPENTCNT:
+		/* Can't do this anymore */
+		return 0;
+	case RNDCLEARPOOL:
+		/* Can't to this anymore */
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+struct file_operations random_fops = {
+	.read		= random_read,
+	.write		= random_write,
+	.poll		= random_poll,
+	.ioctl		= random_ioctl,
+};
+
+struct file_operations urandom_fops = {
+	.read		= urandom_read,
+	.write		= random_write,
+	.ioctl		= random_ioctl,
+};
+
+/***************************************************************
+ * Random UUID interface
+ * 
+ * Used here for a Boot ID, but can be useful for other kernel 
+ * drivers.
+ ***************************************************************/
+
+/*
+ * Generate random UUID
+ */
+void generate_random_uuid(unsigned char uuid_out[16])
+{
+	get_random_bytes(uuid_out, 16);
+	/* Set UUID version to 4 --- truely random generation */
+	uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
+	/* Set the UUID variant to DCE */
+	uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
+}
+
+EXPORT_SYMBOL(generate_random_uuid);
+
+/********************************************************************
+ *
+ * Sysctl interface
+ *
+ ********************************************************************/
+
+#ifdef CONFIG_SYSCTL
+
+#include <linux/sysctl.h>
+
+static int sysctl_poolsize;
+static int min_read_thresh, max_read_thresh;
+static int min_write_thresh, max_write_thresh;
+static char sysctl_bootid[16];
+
+static int proc_do_poolsize(ctl_table *table, int write, struct file *filp,
+			    void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int	ret;
+
+	sysctl_poolsize = POOLBITS;
+
+	ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);
+	if (ret || !write ||
+	    (sysctl_poolsize == POOLBITS))
+		return ret;
+
+	return ret; /* can't change the pool size in fortuna */
+}
+
+static int poolsize_strategy(ctl_table *table, int __user *name, int nlen,
+			     void __user *oldval, size_t __user *oldlenp,
+			     void __user *newval, size_t newlen, void **context)
+{
+	int	len;
+	
+	sysctl_poolsize = POOLBITS;
+
+	/*
+	 * We only handle the write case, since the read case gets
+	 * handled by the default handler (and we don't care if the
+	 * write case happens twice; it's harmless).
+	 */
+	if (newval && newlen) {
+		len = newlen;
+		if (len > table->maxlen)
+			len = table->maxlen;
+		if (copy_from_user(table->data, newval, len))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/*
+ * These functions is used to return both the bootid UUID, and random
+ * UUID.  The difference is in whether table->data is NULL; if it is,
+ * then a new UUID is generated and returned to the user.
+ * 
+ * If the user accesses this via the proc interface, it will be returned
+ * as an ASCII string in the standard UUID format.  If accesses via the 
+ * sysctl system call, it is returned as 16 bytes of binary data.
+ */
+static int proc_do_uuid(ctl_table *table, int write, struct file *filp,
+			void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	ctl_table	fake_table;
+	unsigned char	buf[64], tmp_uuid[16], *uuid;
+
+	uuid = table->data;
+	if (!uuid) {
+		uuid = tmp_uuid;
+		uuid[8] = 0;
+	}
+	if (uuid[8] == 0)
+		generate_random_uuid(uuid);
+
+	sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
+		"%02x%02x%02x%02x%02x%02x",
+		uuid[0],  uuid[1],  uuid[2],  uuid[3],
+		uuid[4],  uuid[5],  uuid[6],  uuid[7],
+		uuid[8],  uuid[9],  uuid[10], uuid[11],
+		uuid[12], uuid[13], uuid[14], uuid[15]);
+	fake_table.data = buf;
+	fake_table.maxlen = sizeof(buf);
+
+	return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos);
+}
+
+static int uuid_strategy(ctl_table *table, int __user *name, int nlen,
+			 void __user *oldval, size_t __user *oldlenp,
+			 void __user *newval, size_t newlen, void **context)
+{
+	unsigned char	tmp_uuid[16], *uuid;
+	unsigned int	len;
+
+	if (!oldval || !oldlenp)
+		return 1;
+
+	uuid = table->data;
+	if (!uuid) {
+		uuid = tmp_uuid;
+		uuid[8] = 0;
+	}
+	if (uuid[8] == 0)
+		generate_random_uuid(uuid);
+
+	if (get_user(len, oldlenp))
+		return -EFAULT;
+	if (len) {
+		if (len > 16)
+			len = 16;
+		if (copy_to_user(oldval, uuid, len) ||
+		    put_user(len, oldlenp))
+			return -EFAULT;
+	}
+	return 1;
+}
+
+ctl_table random_table[] = {
+	{
+		.ctl_name	= RANDOM_POOLSIZE,
+		.procname	= "poolsize",
+		.data		= &sysctl_poolsize,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_do_poolsize,
+		.strategy	= &poolsize_strategy,
+	},
+	{
+		.ctl_name	= RANDOM_ENTROPY_COUNT,
+		.procname	= "entropy_avail",
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
+		.ctl_name	= RANDOM_READ_THRESH,
+		.procname	= "read_wakeup_threshold",
+		.data		= &random_read_wakeup_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &min_read_thresh,
+		.extra2		= &max_read_thresh,
+	},
+	{
+		.ctl_name	= RANDOM_WRITE_THRESH,
+		.procname	= "write_wakeup_threshold",
+		.data		= &random_write_wakeup_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &min_write_thresh,
+		.extra2		= &max_write_thresh,
+	},
+	{
+		.ctl_name	= RANDOM_BOOT_ID,
+		.procname	= "boot_id",
+		.data		= &sysctl_bootid,
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= &proc_do_uuid,
+		.strategy	= &uuid_strategy,
+	},
+	{
+		.ctl_name	= RANDOM_UUID,
+		.procname	= "uuid",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= &proc_do_uuid,
+		.strategy	= &uuid_strategy,
+	},
+	{
+		.ctl_name	= RANDOM_DIGEST_ALGO,
+		.procname	= "digest_algo",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= &proc_dostring,
+	},
+	{
+		.ctl_name	= RANDOM_CIPHER_ALGO,
+		.procname	= "cipher_algo",
+		.maxlen		= 16,
+		.mode		= 0444,
+		.proc_handler	= &proc_dostring,
+	},
+	{ .ctl_name = 0 }
+};
+
+static void sysctl_init_random(struct entropy_store *random_state)
+{
+	int i;
+
+	/* If the sys-admin doesn't want people to know how fast
+	 * random events are happening, he can set the read-threshhold
+	 * down to zero so /dev/random never blocks.  Default is to block.
+	 * This is for the paranoid loonies who think frequency analysis
+	 * would lead to something.
+	 */
+	min_read_thresh = 0;
+	min_write_thresh = 0;
+	max_read_thresh = max_write_thresh = POOLBITS;
+	for (i=0; random_table[i].ctl_name!=0; i++) {
+		switch (random_table[i].ctl_name) {
+			case RANDOM_ENTROPY_COUNT:
+			random_table[i].data = &random_state->entropy_count;
+			break;
+
+			case RANDOM_DIGEST_ALGO:
+			random_table[i].data = (void*)random_state->digestAlgo;
+			break;
+
+			case RANDOM_CIPHER_ALGO:
+			random_table[i].data = (void*)random_state->cipherAlgo;
+			break;
+
+			default:
+			break;
+		}
+	}
+}
+#endif 	/* CONFIG_SYSCTL */
+
+/********************************************************************
+ *
+ * Random funtions for networking
+ *
+ ********************************************************************/
+
+/*
+ * TCP initial sequence number picking.  This uses the random number
+ * generator to pick an initial secret value.  This value is encrypted
+ * with the TCP endpoint information to provide a unique starting point
+ * for each pair of TCP endpoints.  This defeats attacks which rely on
+ * guessing the initial TCP sequence number.  This algorithm was
+ * suggested by Steve Bellovin, modified by Jean-Luc Cooke.
+ *
+ * Using a very strong hash was taking an appreciable amount of the total
+ * TCP connection establishment time, so this is a weaker hash,
+ * compensated for by changing the secret periodically.  This was changed
+ * again by Jean-Luc Cooke to use AES256-CBC encryption which is faster
+ * still (see `/usr/bin/openssl speed md4 sha1 aes`)
+ */
+
+/* This should not be decreased so low that ISNs wrap too fast. */
+#define REKEY_INTERVAL	300
+/*
+ * Bit layout of the tcp sequence numbers (before adding current time):
+ * bit 24-31: increased after every key exchange
+ * bit 0-23: hash(source,dest)
+ *
+ * The implementation is similar to the algorithm described
+ * in the Appendix of RFC 1185, except that
+ * - it uses a 1 MHz clock instead of a 250 kHz clock
+ * - it performs a rekey every 5 minutes, which is equivalent
+ * 	to a (source,dest) tulple dependent forward jump of the
+ * 	clock by 0..2^(HASH_BITS+1)
+ *
+ * Thus the average ISN wraparound time is 68 minutes instead of
+ * 4.55 hours.
+ *
+ * SMP cleanup and lock avoidance with poor man's RCU.
+ * 			Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
+ * 		
+ */
+#define COUNT_BITS	8
+#define COUNT_MASK	( (1<<COUNT_BITS)-1)
+#define HASH_BITS	24
+#define HASH_MASK	( (1<<HASH_BITS)-1 )
+
+static spinlock_t ip_lock = SPIN_LOCK_UNLOCKED;
+static unsigned int ip_cnt, network_count;
+
+static void __check_and_rekey(time_t time)
+{
+	u8 tmp[RANDOM_MAX_KEY_SIZE];
+	spin_lock_bh(&ip_lock);
+
+	get_random_bytes(tmp, random_state->keysize);
+	crypto_cipher_setkey(random_state->networkCipher,
+					(const u8*)tmp,
+					random_state->keysize);
+	random_state->networkCipher_ready = 1;
+	network_count = (ip_cnt & COUNT_MASK) << HASH_BITS;
+	mb();
+	ip_cnt++;
+
+	spin_unlock_bh(&ip_lock);
+	return;
+}
+
+static inline void check_and_rekey(time_t time)
+{
+	static time_t rekey_time=0;
+
+	rmb();
+	if (!rekey_time || (time - rekey_time) > REKEY_INTERVAL) {
+		__check_and_rekey(time);
+		rekey_time = time;
+	}
+
+	return;
+}
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+__u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr,
+				   __u16 sport, __u16 dport)
+{
+	struct timeval 	tv;
+	__u32		seq;
+	u8		tmp[RANDOM_MAX_BLOCK_SIZE];
+	struct scatterlist sgtmp[1];
+
+	/*
+	 * The procedure is the same as for IPv4, but addresses are longer.
+	 * Thus we must use two AES operations.
+	 */
+
+	do_gettimeofday(&tv);	/* We need the usecs below... */
+	check_and_rekey(tv.tv_sec);
+
+	sgtmp[0].page = virt_to_page(tmp);
+	sgtmp[0].offset = offset_in_page(tmp);
+	sgtmp[0].length = random_state->blocksize;
+
+	/*
+	 * AES256 is 2.5 times faster then MD4 by openssl tests.
+	 * We can afford to encrypt 2 block in CBC with
+	 * and IV={(sport)<<16 | dport, 0, 0, 0}
+	 *
+	 * seq = ct[0], ct = Enc-CBC(Key, {ports}, {daddr, saddr});
+	 *                 = Enc(Key, saddr xor Enc(Key, daddr))
+	 */ 
+	
+	/* PT0 = daddr */
+	memcpy(tmp, daddr, random_state->blocksize);
+	/* IV = {ports,0,0,0} */
+	tmp[0] ^= (sport<<16) | dport;
+	crypto_cipher_encrypt(random_state->networkCipher, sgtmp, sgtmp, 1);
+	/* PT1 = saddr */
+	random_state->networkCipher->crt_cipher.cit_xor_block(tmp, (const u8*)saddr);
+	crypto_cipher_encrypt(random_state->networkCipher, sgtmp, sgtmp, 1);
+
+	seq = tmp[0];
+	seq += network_count;
+	seq += tv.tv_usec + tv.tv_sec*1000000;
+
+	return seq;
+}
+EXPORT_SYMBOL(secure_tcpv6_sequence_number);
+
+__u32 secure_ipv6_id(__u32 *daddr)
+{
+	u8 tmp[RANDOM_MAX_BLOCK_SIZE];
+	struct scatterlist sgtmp[1];
+
+	check_and_rekey(get_seconds());
+
+	memcpy(tmp, daddr, random_state->blocksize);
+	sgtmp[0].page = virt_to_page(tmp);
+	sgtmp[0].offset = offset_in_page(tmp);
+	sgtmp[0].length = random_state->blocksize;
+
+	/* id = tmp[0], tmp = Enc(Key, daddr); */
+	crypto_cipher_encrypt(random_state->networkCipher, sgtmp, sgtmp, 1);
+
+	return tmp[0];
+}
+
+EXPORT_SYMBOL(secure_ipv6_id);
+#endif
+
+
+__u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr,
+				 __u16 sport, __u16 dport)
+{
+	struct timeval 	tv;
+	__u32		seq;
+	u8 tmp[RANDOM_MAX_BLOCK_SIZE];
+	struct scatterlist sgtmp[1];
+
+	/*
+	 * Pick a random secret every REKEY_INTERVAL seconds.
+	 */
+	do_gettimeofday(&tv);	/* We need the usecs below... */
+	check_and_rekey(tv.tv_sec);
+
+	/*
+	 *  Pick a unique starting offset for each TCP connection endpoints
+	 *  (saddr, daddr, sport, dport).
+	 *  Note that the words are placed into the starting vector, which is 
+	 *  then mixed with a partial MD4 over random data.
+	 */
+	/*
+	 * AES256 is 2.5 times faster then MD4 by openssl tests.
+	 * We can afford to encrypt 1 block
+	 *
+	 * seq = ct[0], ct = Enc(Key, {(sport<<16)|dport, daddr, saddr, 0})
+	 */ 
+	
+	tmp[0] = (sport<<16) | dport;
+	tmp[1] = daddr;
+	tmp[2] = saddr;
+	tmp[3] = 0;
+	crypto_cipher_encrypt(random_state->networkCipher, sgtmp, sgtmp, 1);
+
+	seq = tmp[0];
+	seq += network_count;
+	/*
+	 *	As close as possible to RFC 793, which
+	 *	suggests using a 250 kHz clock.
+	 *	Further reading shows this assumes 2 Mb/s networks.
+	 *	For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
+	 *	That's funny, Linux has one built in!  Use it!
+	 *	(Networks are faster now - should this be increased?)
+	 */
+	seq += tv.tv_usec + tv.tv_sec*1000000;
+
+#if 0
+	printk("init_seq(%lx, %lx, %d, %d) = %d\n",
+	       saddr, daddr, sport, dport, seq);
+#endif
+	return seq;
+}
+
+EXPORT_SYMBOL(secure_tcp_sequence_number);
+
+/*  The code below is shamelessly stolen from secure_tcp_sequence_number().
+ *  All blames to Andrey V. Savochkin <saw@xxxxxx>.
+ *  Changed by Jean-Luc Cooke <jlcooke@xxxxxxxxxxxxxx> to use AES & C.A.P.I.
+ */
+__u32 secure_ip_id(__u32 daddr)
+{
+	struct scatterlist sgtmp[1];
+	u8 tmp[RANDOM_MAX_BLOCK_SIZE];
+
+	check_and_rekey(get_seconds());
+
+	/*
+	 *  Pick a unique starting offset for each IP destination.
+	 *  id = ct[0], ct = Enc(Key, {daddr,0,0,0});
+	 */
+	tmp[0] = daddr;
+	tmp[1] = 0;
+	tmp[2] = 0;
+	tmp[3] = 0;
+	sgtmp[0].page = virt_to_page(tmp);
+	sgtmp[0].offset = offset_in_page(tmp);
+	sgtmp[0].length = random_state->blocksize;
+
+	crypto_cipher_encrypt(random_state->networkCipher, sgtmp, sgtmp, 1);
+
+	return tmp[0];
+}
+
+#ifdef CONFIG_SYN_COOKIES
+/*
+ * Secure SYN cookie computation. This is the algorithm worked out by
+ * Dan Bernstein and Eric Schenk.
+ *
+ * For linux I implement the 1 minute counter by looking at the jiffies clock.
+ * The count is passed in as a parameter, so this code doesn't much care.
+ * 
+ * SYN cookie (and seq# & id#) Changed in 2004 by Jean-Luc Cooke
+ * <jlcooke@xxxxxxxxxxxxxx> to use the C.A.P.I. and AES256.
+ */
+
+#define COOKIEBITS 24	/* Upper bits store count */
+#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
+
+__u32 secure_tcp_syn_cookie(__u32 saddr, __u32 daddr, __u16 sport,
+		__u16 dport, __u32 sseq, __u32 count, __u32 data)
+{
+	struct scatterlist sg[1];
+	__u32   tmp[4];
+
+	/*
+	 * Compute the secure sequence number.
+	 *
+	 * Output is the 32bit tag of a CBC-MAC of
+	 * PT={count,0,0,0} with IV={addr,daddr,sport|dport,sseq}
+	 *   cookie = {<8bit count>,
+	 *             truncate_24bit(
+	 *               Encrypt(Sec, {saddr,daddr,sport|dport,sseq})
+	 *             )
+	 *            }
+	 *
+	 * DJB wrote (http://cr.yp.to/syncookies/archive) about how to do this
+	 * with hash algorithms.
+	 * - we can replace two SHA1s used in the previous kernel with 1 AES
+	 *   and make things 5x faster
+	 * - I'd like to propose we remove the use of two whittenings with a
+	 *   single operation since we were only using addition modulo 2^32 of
+	 *   all these values anyways.  Not to mention the hashs differ only in
+	 *   that the second processes more data... why drop the first hash?
+	 *   We did learn that addition is commutative and associative long ago.
+	 * - by replacing two SHA1s and addition modulo 2^32 with encryption of
+	 *   a 32bit value using CAPI we've made it 1,000,000,000 times easier
+	 *   to understand what is going on.
+	 */
+
+	tmp[0] = saddr;
+	tmp[1] = daddr;
+	tmp[2] = (sport << 16) + dport;
+	tmp[3] = sseq;
+
+	sg[0].page = virt_to_page(tmp);
+	sg[0].offset = offset_in_page(tmp);
+	sg[0].length = random_state->blocksize;
+	if (!random_state->networkCipher_ready) {
+		check_and_rekey(get_seconds());
+	}
+	/* tmp[]/sg[0] = Enc(Sec, {saddr,daddr,sport|dport,sseq}) */
+	crypto_cipher_encrypt(random_state->networkCipher, sg, sg, 1);
+
+	/* cookie = CTR encrypt of 8-bit-count and 24-bit-data */
+	return tmp[0] ^ ( (count << COOKIEBITS) | (data & COOKIEMASK) );
+}
+
+/*
+ * This retrieves the small "data" value from the syncookie.
+ * If the syncookie is bad, the data returned will be out of
+ * range.  This must be checked by the caller.
+ *
+ * The count value used to generate the cookie must be within
+ * "maxdiff" if the current (passed-in) "count".  The return value
+ * is (__u32)-1 if this test fails.
+ */
+__u32 check_tcp_syn_cookie(__u32 cookie, __u32 saddr, __u32 daddr, __u16 sport,
+		__u16 dport, __u32 sseq, __u32 count, __u32 maxdiff)
+{
+	struct scatterlist sg[1];
+	__u32 tmp[4], thiscount, diff;
+
+	if (random_state == NULL  ||  !random_state->networkCipher_ready)
+		return (__u32)-1;       /* Well, duh! */
+
+	tmp[0] = saddr;
+	tmp[1] = daddr;
+	tmp[2] = (sport << 16) + dport;
+	tmp[3] = sseq;
+	sg[0].page = virt_to_page(tmp);
+	sg[0].offset = offset_in_page(tmp);
+	sg[0].length = random_state->blocksize;
+	crypto_cipher_encrypt(random_state->networkCipher, sg, sg, 1);
+
+	/* CTR decrypt the cookie */
+	cookie ^= tmp[0];
+
+	/* top 8 bits are 'count' */
+	thiscount = cookie >> COOKIEBITS;
+
+	diff = count - thiscount;
+	if (diff >= maxdiff)
+		return (__u32)-1;
+
+	/* bottom 24 bits are 'data' */
+	return cookie & COOKIEMASK;
+}
+#endif
diff -X exclude -Nur linux-2.6.8.1/drivers/char/random.c linux-2.6.8.1-rand2/drivers/char/random.c
--- linux-2.6.8.1/drivers/char/random.c	2004-09-27 16:04:53.000000000 -0400
+++ linux-2.6.8.1-rand2/drivers/char/random.c	2004-09-28 23:25:46.000000000 -0400
@@ -261,6 +261,17 @@
 #include <asm/io.h>
 
 /*
+ * In September 2004, Jean-Luc Cooke wrote a Fortuna RNG for Linux
+ * which was non-blocking and used the Cryptographic API.
+ * We use it now if the user wishes.
+ */
+#ifdef CONFIG_CRYPTO_RANDOM_FORTUNA
+	#warning using the Fortuna PRNG for /dev/random
+	#include "../crypto/random-fortuna.c"
+#else /* CONFIG_CRYPTO_RANDOM_FORTUNA */
+	#warning using the Linux Legacy PRNG for /dev/random
+
+/*
  * Configuration information
  */
 #define DEFAULT_POOL_SIZE 512
@@ -2483,3 +2494,5 @@
 	return (cookie - tmp[17]) & COOKIEMASK;	/* Leaving the data behind */
 }
 #endif
+
+#endif /* CONFIG_CRYPTO_RANDOM_FORTUNA */
diff -X exclude -Nur linux-2.6.8.1/include/linux/sysctl.h linux-2.6.8.1-rand2/include/linux/sysctl.h
--- linux-2.6.8.1/include/linux/sysctl.h	2004-08-14 06:55:33.000000000 -0400
+++ linux-2.6.8.1-rand2/include/linux/sysctl.h	2004-09-29 10:45:20.592695040 -0400
@@ -198,7 +198,9 @@
 	RANDOM_READ_THRESH=3,
 	RANDOM_WRITE_THRESH=4,
 	RANDOM_BOOT_ID=5,
-	RANDOM_UUID=6
+	RANDOM_UUID=6,
+	RANDOM_DIGEST_ALGO=7,
+	RANDOM_CIPHER_ALGO=8
 };
 
 /* /proc/sys/kernel/pty */