What is the HASH Message Digest Framework in PHP?

[jhon]

Hi everyone,
I am learning an advanced topics in PHP programming language. Now I am doing the Cryptography Extensions in PHP. In that I am not able to understand the HASH, which is the message digest framework in PHP? So I am posting here my query, so that I can get needful help from you guys.!! Please explain me what is the HASH Message Digest Framework in PHP? Any other information about the HASH would be grateful.!!

[Allan.d]

The HASH is like an engine thumbprint. Allows direct or incremental processing of arbitrary size message using a variety of algorithms. The Hash extension requires no external libraries and is enabled by default since PHP 5.1.2. It must be explicitly disabled at compile time with - disable-hash. For older versions of PHP, you must install the "module PECL extension to use the Hash. HASH Message Digest Framework does the Native implementations of common message digest algorithms using a generic factory method.

[Solitario]

There is no installation needed to use these functions, they are part of the PHP core. You should keep in mind that this extension does not define any configuration directive. This extension defines one resource Hash of context returned by hash_init (). The function hash_init initialize an incremental hashing context. The following is a description for the same :

hash_init resource (string $ algo [, int $ options = 0 [, string $ key = NULL]])

[Deabelos]

Even I would like to discuss on the hash_init. The hash_init can take the following parameters :

1. algo - Name of selected hashing algorithm.
2. Options - Optional configurations for generating the hash, currently supports only one option: HASH_HMAC. When this option is specified, the key must be specified.
3. key - When HASH_HMAC is specified for options, a shared secret key to be used with the HMAC hash method must be provided in this setting.

Returns a hash of context for use with hash_update (), hash_update_stream (), hash_update_file () and hash_final ().

[void]

I have given you an example of incremental hashing. Hope that you can understand much better after looking at the example given below :

<?php
$ctx = hash_init('md3');
hash_update($ctx, 'This is  ');
hash_update($ctx, 'an example.');
echo hash_final($ctx);
?>

[kelfro]

The following is the list of the Hash Functions with their descriptions :

• hash_algos - Returns a list of registered hashing algorithms
• hash_copy - Copy hashing context
• hash_file - Generate a hash value using the contents of a given file
• hash_final - Finalize an incremental hash and return the result of the fingerprint
• hash_hmac_file - Generates a key value hash using the HMAC method and content of a given file