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(PHP 4 >= 4.0.2, PHP 5)
mcrypt_generic_init — This function initializes all buffers needed for encryption
You need to call this function before every call to mcrypt_generic() or mdecrypt_generic().
The encryption descriptor.
The maximum length of the key should be the one obtained by calling mcrypt_enc_get_key_size() and every value smaller than this is legal.
The IV should normally have the size of the algorithms block size, but you must obtain the size by calling mcrypt_enc_get_iv_size(). IV is ignored in ECB. IV MUST exist in CFB, CBC, STREAM, nOFB and OFB modes. It needs to be random and unique (but not secret). The same IV must be used for encryption/decryption. If you do not want to use it you should set it to zeros, but this is not recommended.
The function returns a negative value on error: -3 when the key length was incorrect, -4 when there was a memory allocation problem and any other return value is an unknown error. If an error occurs a warning will be displayed accordingly. FALSE is returned if incorrect parameters were passed.
If you write error-checking into your code, be warned that this function returns FALSE on some errors, and 0 on success, hence
mcrypt_generic_init( $a, $b, $c ) or die( "Oops");
ALWAYS exits with the error message "Oops", and
(mcrypt_generic_init( $a, $b, $c ) >= 0 ) or die( "Oops");
Sometimes continues when mcrypt_generic_init() actually failed.
To check for successful init use something like:
$s = mcrypt_generic_init( $a, $b, $c );
if( ($s < 0) || ($s === false))
die( "Really an error" );
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