(Node.js) AEAD AES 128-bit GCM

Demonstrates AES encryption using the Galois/Counter Mode (GCM). GCM is an authenticated encryption mode with "additional data" (often referred to as AEAD). GCM is a cipher mode that can be applied to any symmetric encryption algorithm with a 16-byte block size, such as AES and Twofish. In GCM mode, the block encryption algorithm is transformed into a stream encryption algorithm, and therefore no padding occurs (and the PaddingScheme property does not apply). The "additional data" (known as the AAD) does not get encrypted but plays a role in the computation of the resulting "authenticated tag".

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    var crypt = new chilkat.Crypt2();

    // Set the encryption algorithm to "AES"	
    crypt.CryptAlgorithm = "aes";

    // Indicate that the Galois/Counter Mode (GCM) should be used:
    crypt.CipherMode = "gcm";

    // KeyLength may be 128, 192, 256
    crypt.KeyLength = 128;

    // This is the 128-bit AES secret key (in hex format)
    var K = "feffe9928665731c6d6a8f9467308308";

    // This is the 16-byte initialization vector:
    var IV = "cafebabefacedbaddecaf888";

    // This is the additional data to be used as input to the GCM AEAD algorithm,
    // but is not included in the output.  It plays a role in the computation of the
    // resulting authenticated tag.
    var AAD = "feedfacedeadbeeffeedfacedeadbeefabaddad2";

    // The plain-text bytes (in hex format) to be encrypted.
    var PT = "d9313225f88406e5a55909c5aff5269a86a7a9531534f7da2e4c303d8a318a721c3c0c95956809532fcf0e2449a6b525b16aedf5aa0de657ba637b39";

    // The expected cipher text (in hex format)
    var CT = "42831ec2217774244b7221b784d0d49ce3aa212f2c02a4e035c17e2329aca12e21d514b25466931c7d8f6a5aac84aa051ba30b396a0aac973d58e091";

    // The expected authenticated tag given the above inputs.
    var T = "5bc94fbc3221a5db94fae95ae7121a47";

    // Note: The above data are the values for test vector #4 from 
    // the PDF document at: http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-spec.pdf

    // EncodingMode specifies the encoding of the output for
    // encryption, and the input for decryption.
    // It may be "hex", "url", "base64", or "quoted-printable".
    crypt.EncodingMode = "hex";

    // Set the secret key and IV
    crypt.SetEncodedIV(IV,"hex");
    crypt.SetEncodedKey(K,"hex");

    // Set the additional authenticated data (AAD)
    var success = crypt.SetEncodedAad(AAD,"hex");

    // For the purpose of duplicating the test vectors, we are using the EncryptEncoded method.
    // This method decodes the input string according to the encoding specified by the EncodingMode
    // property, which in this case is "hex".  The decoded bytes are encrypted using the mode specified
    // by the CipherMode property.  The resulting
    // encrypted bytes are encoded (again using the encoding mode specified by EncodingMode),
    // and the result is returned.
    // <b>Note:</b> The CipherMode property sets the block mode of operation (gcm, cfb, cbc, ofb, ecb, etc.) 
    // for any of the Chilkat encryption/decryption methods (such as EncryptBytes, EncryptString, 
    // CkEncryptFile, etc.)   Just because GCM mode is demonstrated with EncryptEncoded/DecryptEncoded,
    // does not imply that GCM mode is specific to only these methods.
    var ctResult = crypt.EncryptEncoded(PT);
    if (crypt.LastMethodSuccess !== true) {
        console.log(crypt.LastErrorText);
        return;
    }

    // Examine the result.  It should be the same (case insensitive) as our expected result:
    console.log("computed result: " + ctResult);
    console.log("expected result: " + CT);

    // Examine the authenticated tag. It should be the same (case insensitive) as our expected authenticated tag:
    var tResult = crypt.GetEncodedAuthTag("hex");
    console.log("computed authTag: " + tResult);
    console.log("expected authTag: " + T);

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

    // 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 (case insensitive) to 
    // the expected result.
    // Note: The return value of SetEncodedAuthTag indicates whether the string passed was a valid
    // representation of the encoding specified in the 2nd arg.
    success = crypt.SetEncodedAuthTag(T,"hex");

    // All of our properties (IV, secret key, cipher mode, and AAD) are already set from the code above...

    // So let's decrypt CT to and check to see if we get PT.
    var ptResult = crypt.DecryptEncoded(CT);
    if (crypt.LastMethodSuccess !== true) {
        // Failed.  The resultant authenticated tag did not equal the expected authentication tag.
        console.log(crypt.LastErrorText);
        return;
    }

    // Examine the decrypted result.  It should be the same as our expected plaintext (case insensitive)
    console.log("plaintext decrypted: " + ptResult);
    console.log("plaintext expected:  " + PT);

    // Let's intentionally set the expected authenticated tag to an incorrect value. 
    // The decrypt operation should fail:
    var tInvalid = "ffaabbbc3221a5db94fae95ae7121a47";

    success = crypt.SetEncodedAuthTag(tInvalid,"hex");

    ptResult = crypt.DecryptEncoded(CT);
    if (crypt.LastMethodSuccess !== true) {
        // Failed.  The resultant authenticated tag did not equal the expected authentication tag.
        console.log(crypt.LastErrorText);
    }


}

chilkatExample();