On 14 May 2013 14:44, yassine ahmed <[email protected]> wrote:
> hi all,
> please i don't know how calculate the icv (Integrity Check Value). used in
> aes-gcm algorithm

The "Integrity Check Value" is known as the authentication tag.

In order to retrieve the tag you must call EVP_CIPHER_CTX_ctrl with a
"type" argument of EVP_CTRL_GCM_GET_TAG. A full example is available
here:

http://wiki.opensslfoundation.com/index.php/EVP_Authenticated_Encryption_and_Decryption

Also see the openssl manual:
http://wiki.opensslfoundation.com/index.php/Manual:EVP_EncryptInit%283%29#GCM_Mode

Matt
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