PHP 5.6.24 is released

mcrypt_get_iv_size

(PHP 4 >= 4.0.2, PHP 5, PHP 7)

mcrypt_get_iv_sizeReturns the size of the IV belonging to a specific cipher/mode combination

Descrição

int mcrypt_get_iv_size ( string $cipher , string $mode )

Gets the size of the IV belonging to a specific cipher/mode combination.

It is more useful to use the mcrypt_enc_get_iv_size() function as this uses the resource returned by mcrypt_module_open().

Parâmetros

cipher

Uma das constantes MCRYPT_ciphername, ou o nome do algoritmo como string.

mode

Uma das constantes MCRYPT_MODE_modename, ou uma das strings: "ecb", "cbc", "cfb", "ofb", "nofb" ou "stream".

The IV is ignored in ECB mode as this mode does not require it. You will need to have the same IV (think: starting point) both at encryption and decryption stages, otherwise your encryption will fail.

Valor Retornado

Returns the size of the Initialization Vector (IV) in bytes. On error the function returns FALSE. If the IV is ignored in the specified cipher/mode combination zero is returned.

Exemplos

Exemplo #1 mcrypt_get_iv_size() Example

<?php
    
echo mcrypt_get_iv_size(MCRYPT_CAST_256MCRYPT_MODE_CFB) . "\n";

    echo 
mcrypt_get_iv_size('des''ecb') . "\n";
?>

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Hernanibus
29 days ago
The size of the initialization vector (iv) will be returned in bytes NOT bits, something to keep in mind specially if the iv is passed together appended or prepended with the encrypted data for decryption
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