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rsEncrypt()

Description

Encrypts data


@todo Add a fourth parameter to use with custom metadata (NOT ResourceSpace metadata) for generating MAC. this should
add extra security by making MAC harder to be forged

Parameters

ColumnTypeDefaultDescription
$data string Data to be encypted
$key string Key to use
$keylength string 128 Optional key length

Return

string Encrypted data

Location

include/encryption_functions.php lines 16 to 52

Definition

 
function rsEncrypt($data, $key, $keylength = 128)
{
    global $scramble_key;

    /*
    Encrypt-then-MAC (EtM)
    ======================
    PlainText
        |
    Encryption <-- Key
        |_________   |
        |         |  |
        |      HashFunction
        |           |
    --------------------
    | Ciphertext | MAC |
    --------------------
    The plaintext is first encrypted, then a MAC is produced based on the resulting ciphertext.  The ciphertext and its
    MAC are sent together.
    */
    $method  = "AES-128-CTR";
    $options = OPENSSL_RAW_DATA;
    $nonce   = generateSecureKey($keylength);

    // Get 2 derived subkeys, one for message authentication code (MAC) and the other one for encryption/ decryption.
    $mac_key = hash_hmac("sha256", "mac_key", $scramble_key, true);
    $enc_key = hash_hmac("sha256", "enc_key", $scramble_key, true);

    // Synthetic Initialization Vector (SIV)
    $siv = substr(hash_hmac("sha256", "{$nonce}{$scramble_key}{$key}", $mac_key, true), 0, 16);

    $cyphertext = bin2hex(openssl_encrypt($data, $method, $enc_key, $options, $siv));

    $mac = hash_hmac("sha256", "{$cyphertext}{$nonce}{$scramble_key}", $mac_key);

    return "{$nonce}@@{$cyphertext}@@{$mac}";
}

This article was last updated 11th February 2025 18:35 Europe/London time based on the source file dated 21st January 2025 15:20 Europe/London time.