hash_pbkdf2(3) [php man page]

HASH_PBKDF2(3)								 1							    HASH_PBKDF2(3)

hash_pbkdf2 - Generate a PBKDF2 key derivation of a supplied password

SYNOPSIS

       string hash_pbkdf2 (string  $algo, string  $password, string  $salt, int  $iterations, [int  $length], [bool  $raw_output = false])

DESCRIPTION

PARAMETERS

	      o $algo
		- Name of selected hashing algorithm (i.e.  md5, sha256, haval160,4, etc..) See hash_algos(3) for a list of supported algorithms.

	      o $password
		- The password to use for the derivation.

	      o $salt
		- The salt to use for the derivation. This value should be generated randomly.

	      o $iterations
		- The number of internal iterations to perform for the derivation.

	      o $length
		-  The	length of the output string. If $raw_output is TRUE this corresponds to the byte-length of the derived key, if $raw_output
		is FALSE this corresponds to twice the byte-length of the derived key (as every byte of the key is returned as two hexits).  If  0
		is passed, the entire output of the supplied algorithm is used.

	      o $raw_output
		- When set to TRUE, outputs raw binary data.  FALSE outputs lowercase hexits.

RETURN VALUES

	Returns a string containing the derived key as lowercase hexits unless $raw_output is set to TRUE in which case the raw binary representa-
       tion of the derived key is returned.

ERRORS
/EXCEPTIONS
	An E_WARNING will be raised if the algorithm is unknown, the $iterations parameter is less than or equal to 0, the $length is less than  0
       or the $salt is too long (greater than INT_MAX
	- 4).

EXAMPLES

       Example #1

	      hash_pbkdf2(3) example, basic usage

	      <?php
	      $password = "password";
	      $iterations = 1000;

	      // Generate a random IV using mcrypt_create_iv(),
	      // openssl_random_pseudo_bytes() or another suitable source of randomness
	      $salt = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);

	      $hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
	      echo $hash;
	      ?>

	      The above example will output something similar to:

	      120fb6cffcf8b32c43e7

NOTES

       Caution

	       The PBKDF2 method can be used for hashing passwords for storage. However, it should be noted that password_hash(3) or crypt(3) with
	      CRYPT_BLOWFISH are better suited for password storage.

SEE ALSO

       crypt(3), password_hash(3), hash(3), hash_algos(3), hash_init(3), hash_hmac(3), hash_hmac_file(3).

PHP Documentation Group 													    HASH_PBKDF2(3)

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EVP_BytesToKey(3)						      OpenSSL							 EVP_BytesToKey(3)

NAME

       EVP_BytesToKey - password based encryption routine

LIBRARY

       libcrypto, -lcrypto

SYNOPSIS

	#include <openssl/evp.h>

	int EVP_BytesToKey(const EVP_CIPHER *type,const EVP_MD *md,
			      const unsigned char *salt,
			      const unsigned char *data, int datal, int count,
			      unsigned char *key,unsigned char *iv);

DESCRIPTION

       EVP_BytesToKey() derives a key and IV from various parameters. type is the cipher to derive the key and IV for. md is the message digest to
       use.  The salt parameter is used as a salt in the derivation: it should point to an 8 byte buffer or NULL if no salt is used. data is a
       buffer containing datal bytes which is used to derive the keying data. count is the iteration count to use. The derived key and IV will be
       written to key and iv respectively.

NOTES

       A typical application of this function is to derive keying material for an encryption algorithm from a password in the data parameter.

       Increasing the count parameter slows down the algorithm which makes it harder for an attacker to peform a brute force attack using a large
       number of candidate passwords.

       If the total key and IV length is less than the digest length and MD5 is used then the derivation algorithm is compatible with PKCS#5 v1.5
       otherwise a non standard extension is used to derive the extra data.

       Newer applications should use more standard algorithms such as PKCS#5 v2.0 for key derivation.

KEY DERIVATION ALGORITHM

       The key and IV is derived by concatenating D_1, D_2, etc until enough data is available for the key and IV. D_i is defined as:

	       D_i = HASH^count(D_(i-1) || data || salt)

       where || denotes concatentaion, D_0 is empty, HASH is the digest algorithm in use, HASH^1(data) is simply HASH(data), HASH^2(data) is
       HASH(HASH(data)) and so on.

       The initial bytes are used for the key and the subsequent bytes for the IV.

RETURN VALUES

       EVP_BytesToKey() returns the size of the derived key in bytes.

SEE ALSO

       openssl_evp(3), openssl_rand(3), EVP_EncryptInit(3)

HISTORY

1.0.1i								    2014-04-08							 EVP_BytesToKey(3)

Linux and UNIX Man Pages

hash_pbkdf2(3) [php man page]

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