Unable to decrypt aes-192-gcm

Question

I'm using nodejs to encrypt and decrypt aes-192-gcm

here's my code:

const encrypted = decrypt.encryptText('aes-192-gcm', 'FnpkKuIoqZL5B3tnE0Htmg==', '1z3FtB6OitmFOIsP', 'helloWorld', 'base64');
const de = decrypt.decryptText('aes-192-gcm', 'FnpkKuIoqZL5B3tnE0Htmg==', '1z3FtB6OitmFOIsP', encrypted, 'utf-8');
console.log(encrypted);
console.log(de);

Functions used:

 function encryptText(cipher_alg, key, iv, text, encoding) {

        var cipher = crypto.createCipheriv(cipher_alg, key, iv);

        encoding = encoding || "binary";

        var result = cipher.update(text, "utf8", encoding);
        result += cipher.final(encoding);

        return result;
    }

    function decryptText(cipher_alg, key, iv, text, encoding) {

        const decipher = crypto.createDecipheriv(cipher_alg, key, iv);

        encoding = encoding || "binary";

        let result = decipher.update(text, encoding);
        result += decipher.final();

        return result;
    }

The error I'm getting:

Unsupported state or unable to authenticate data

karthick · Answer 1 · 2019-08-01T17:39:00.300

Couple of problems

you are passing a wrong encoding format for the decryptText()
AuthTag is required when using GCM, CCM and OCB.

I have attached a sample code based on the snippet you have shared.

var cipherTag;

const encrypted = encryptText('aes-192-gcm', 'FnpkKuIoqZL5B3tnE0Htmg==', '1z3FtB6OitmFOIsP', 'helloWorld', 'base64');
const de = decryptText('aes-192-gcm', 'FnpkKuIoqZL5B3tnE0Htmg==', '1z3FtB6OitmFOIsP', encrypted, 'base64');
console.log(encrypted);
console.log(de);

function encryptText(cipher_alg, key, iv, text, encoding) {

    var cipher = crypto.createCipheriv(cipher_alg, key, iv);

    encoding = encoding || "binary";

    var result = cipher.update(text, "utf8", encoding);
    result += cipher.final(encoding);
    cipherTag = cipher.getAuthTag();
    return result;
}

function decryptText(cipher_alg, key, iv, text, encoding) {

    const decipher = crypto.createDecipheriv(cipher_alg, key, iv);

    encoding = encoding || "binary";
    decipher.setAuthTag(cipherTag);
    let result = decipher.update(text, encoding, 'utf8');
    result+= decipher.final('utf8');
    return result.toString();
}

// Will output

b2SMQRBt/EgNgQ==
helloWorld

I don't think setAAD is required here, the problem is she is missing the authTag — Adam, Aug 01 '19 at 03:38

score 2 · Answer 2 · answered Jul 31 '19 at 22:28

The crypto module of NodeJS uses OpenSSL. This API has special parameters for GCM / AEAD ciphers. Methods to use them have been added to the API, such as getAuthTag and setAuthTag. Without the latter, the method always throws an exception for GCM mode decryption. The tag is (fortunately) not considered part of the ciphertext in NodeJS / OpenSSL. Other languages runtimes - such as Java - do consider it part of the ciphertext.

Unable to decrypt aes-192-gcm

2 Answers2