CODEWITHSUNDEEP
aes-gcmencryption
Jeniffer
Jeniffer

Reputation:

Unable to decrypt aes-192-gcm

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

Upvotes: 2

Views: 789

Answers (2)

karthick
karthick

Reputation: 12176

Couple of problems

  1. you are passing a wrong encoding format for the decryptText()
  2. 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

Upvotes: 2

Maarten Bodewes
Maarten Bodewes

Reputation: 94078

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.

Upvotes: 2

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