HPAVKeyDAK.c

/*====================================================================*
 *
 *   Copyright (c) 2013 Qualcomm Atheros, Inc.
 *
 *   All rights reserved.
 *
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 *   without modification, are permitted (subject to the limitations
 *   in the disclaimer below) provided that the following conditions
 *   are met:
 *
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 *     notice, this list of conditions and the following disclaimer.
 *
 *   * 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.
 *
 *   * Neither the name of Qualcomm Atheros nor the names of
 *     its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written
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 *   GRANTED BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE
 *   COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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 *   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 *--------------------------------------------------------------------*/

/*====================================================================*
 *
 *   void HPAVKeyDAK (uint8_t DAK [], const char * string);
 *
 *   HPAVKey.h
 *
 *   compute the HomePlugAV compliant Device Access Key (DAK) for a
 *   NUL terminated string; return the key in buffer DAK[]; the key
 *   will be HPAVKEY_DAK_LEN bytes as defined in HPAVKey.h;
 *
 *   seed the digest then salt the digest then rehash the digest 999
 *   times per HomePlug AV Specification;
 *
 *
 *   Contributor(s);
 *	Charles Maier
 *
 *--------------------------------------------------------------------*/

#ifndef HPAVKEYDAK_SOURCE
#define HPAVKEYDAK_SOURCE

#include <memory.h>

#include "../key/HPAVKey.h"
#include "../key/SHA256.h"

void HPAVKeyDAK (uint8_t DAK [], const char * string)

{
	struct sha256 sha256;
	uint8_t digest [SHA256_DIGEST_LENGTH];
	const uint8_t secret [] =
	{
		0x08,
		0x85,
		0x6D,
		0xAF,
		0x7C,
		0xF5,
		0x81,
		0x85
	};
	unsigned rehash = 999;
	SHA256Reset (&sha256);
	SHA256Write (&sha256, string, strlen (string));
	SHA256Write (&sha256, secret, sizeof (secret));
	SHA256Fetch (&sha256, digest);
	while (rehash--)
	{
		SHA256Reset (&sha256);
		SHA256Write (&sha256, digest, sizeof (digest));
		SHA256Fetch (&sha256, digest);
	}
	memcpy (DAK, digest, HPAVKEY_DAK_LEN);
	return;
}


#endif