Node.js

Example: Crypt2.RandomizeIV method

Demonstrates using a random initialization vector for AES GCM encryption. Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    //  This example assumes the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    var crypt = new chilkat.Crypt2();

    crypt.CryptAlgorithm = "aes";
    crypt.CipherMode = "gcm";
    crypt.KeyLength = 256;

    var K = "000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F";
    var AAD = "feedfacedeadbeeffeedfacedeadbeefabaddad2";
    var PT = "This is the text to be AES-GCM encrypted.";

    //  Generate a random IV.
    crypt.RandomizeIV();
    var IV = crypt.GetEncodedIV("hex");

    crypt.SetEncodedKey(K,"hex");

    success = crypt.SetEncodedAad(AAD,"hex");

    //  Return the encrypted bytes as base64
    crypt.EncodingMode = "base64";
    crypt.Charset = "utf-8";
    var cipherText = crypt.EncryptStringENC(PT);
    if (crypt.LastMethodSuccess !== true) {
        console.log(crypt.LastErrorText);
        return;
    }

    //  Get the GCM authenticated tag computed when encrypting.
    var authTag = crypt.GetEncodedAuthTag("base64");

    console.log("Cipher Text: " + cipherText);
    console.log("Auth Tag: " + authTag);

    //  Let's send the IV, CipherText, and AuthTag to the decrypting party.
    //  We'll send them concatenated like this: [IV || Ciphertext || AuthTag]
    //  In base64 format.
    var bdEncrypted = new chilkat.BinData();
    bdEncrypted.AppendEncoded(IV,"hex");
    bdEncrypted.AppendEncoded(cipherText,"base64");
    bdEncrypted.AppendEncoded(authTag,"base64");

    var concatenatedGcmOutput = bdEncrypted.GetEncoded("base64");
    console.log("Concatenated GCM Output: " + concatenatedGcmOutput);

    //  Sample output so far:

    //  -------------------------------------------------------------------------------------
    //  Now let's GCM decrypt...
    //  -------------------------------------------------------------------------------------

    var decrypt = new chilkat.Crypt2();

    //  The values shared and agreed upon by both sides beforehand are: algorithm, cipher mode, secret key, and AAD.
    //  Sometimes the IV can be a value already known and agreed upon, but in this case the encryptor sends the IV to the decryptor.
    decrypt.CryptAlgorithm = "aes";
    decrypt.CipherMode = "gcm";
    decrypt.KeyLength = 256;
    decrypt.SetEncodedKey(K,"hex");
    decrypt.SetEncodedAad(AAD,"hex");

    var bdFromEncryptor = new chilkat.BinData();
    bdFromEncryptor.AppendEncoded(concatenatedGcmOutput,"base64");

    var sz = bdFromEncryptor.NumBytes;

    //  Extract the parts.
    var extractedIV = bdFromEncryptor.GetEncodedChunk(0,16,"hex");
    var extractedCipherText = bdFromEncryptor.GetEncodedChunk(16,sz - 32,"base64");
    var expectedAuthTag = bdFromEncryptor.GetEncodedChunk(sz - 16,16,"base64");

    //  Before GCM decrypting, we must set the authenticated tag to the value that is expected.
    //  The decryption will fail if the resulting authenticated tag is not equal to the expected result.
    success = decrypt.SetEncodedAuthTag(expectedAuthTag,"base64");

    //  Also set the IV.
    decrypt.SetEncodedIV(extractedIV,"hex");

    //  Decrypt..
    decrypt.EncodingMode = "base64";
    decrypt.Charset = "utf-8";
    var decryptedText = decrypt.DecryptStringENC(extractedCipherText);
    if (decrypt.LastMethodSuccess !== true) {
        //  Failed.  The resultant authenticated tag did not equal the expected authentication tag.
        console.log(decrypt.LastErrorText);
        return;
    }

    console.log("Decrypted: " + decryptedText);

}

chilkatExample();