php man page for mcrypt_generic_init

MCRYPT_GENERIC_INIT(3)							 1						    MCRYPT_GENERIC_INIT(3)

mcrypt_generic_init - This function initializes all buffers needed for encryption

SYNOPSIS
       int mcrypt_generic_init (resource  $td, string  $key, string  $iv)

DESCRIPTION
	You need to call this function before every call to mcrypt_generic(3) or mdecrypt_generic(3).

PARAMETERS
	      o $td
		- The encryption descriptor.

	      o $key
		- The maximum length of the key should be the one obtained by calling mcrypt_enc_get_key_size(3) and every value smaller than this
		is legal.

	      o $iv
		-  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(3).  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.

RETURN VALUES
	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.

SEE ALSO
       mcrypt_module_open(3).

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