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75 lines
2.9 KiB
C
75 lines
2.9 KiB
C
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/*
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---------------------------------------------------------------------------
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Copyright (c) 2002, Dr Brian Gladman < >, Worcester, UK.
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All rights reserved.
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LICENSE TERMS
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The free distribution and use of this software in both source and binary
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form is allowed (with or without changes) provided that:
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1. distributions of this source code include the above copyright
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notice, this list of conditions and the following disclaimer;
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2. distributions in binary form include the above copyright
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notice, this list of conditions and the following disclaimer
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in the documentation and/or other associated materials;
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3. the copyright holder's name is not used to endorse products
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built using this software without specific written permission.
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ALTERNATIVELY, provided that this notice is retained in full, this product
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may be distributed under the terms of the GNU General Public License (GPL),
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in which case the provisions of the GPL apply INSTEAD OF those given above.
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DISCLAIMER
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This software is provided 'as is' with no explicit or implied warranties
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in respect of its properties, including, but not limited to, correctness
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and/or fitness for purpose.
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---------------------------------------------------------------------------
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Issue Date: 24/01/2003
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This is the header file for an implementation of a random data pool based on
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the use of an external entropy function (inspired by Peter Gutmann's work).
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*/
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#ifndef _PRNG_H
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#define _PRNG_H
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#include "sha1.h"
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#define PRNG_POOL_LEN 256 /* minimum random pool size */
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#define PRNG_MIN_MIX 20 /* min initial pool mixing iterations */
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/* ensure that pool length is a multiple of the SHA1 digest size */
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#define PRNG_POOL_SIZE (SHA1_DIGEST_SIZE * (1 + (PRNG_POOL_LEN - 1) / SHA1_DIGEST_SIZE))
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/* A function for providing entropy is a parameter in the prng_init() */
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/* call. This function has the following form and returns a maximum */
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/* of 'len' bytes of pseudo random data in the buffer 'buf'. It can */
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/* return less than 'len' bytes but will be repeatedly called for more */
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/* data in this case. */
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typedef int (*prng_entropy_fn)(unsigned char buf[], unsigned int len);
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typedef struct
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{ unsigned char rbuf[PRNG_POOL_SIZE]; /* the random pool */
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unsigned char obuf[PRNG_POOL_SIZE]; /* pool output buffer */
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unsigned int pos; /* output buffer position */
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prng_entropy_fn entropy; /* entropy function pointer */
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} prng_ctx;
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/* initialise the random stream generator */
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void prng_init(prng_entropy_fn fun, prng_ctx ctx[1]);
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/* obtain random bytes from the generator */
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void prng_rand(unsigned char data[], unsigned int data_len, prng_ctx ctx[1]);
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/* close the random stream generator */
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void prng_end(prng_ctx ctx[1]);
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#endif
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