RSA private key unable to decrypt data

Question

I'm using JavaScript and Node.js to work on a sort of messaging project. When a user is created, the server uses the Node.js crypto library to generate an RSA keypair. The private key is encrypted using the users password. On the webapp, when User A sends a message to User B, the data is encrypted using User B's public key. When User B receives the message, it is decrypted using their private key and password.

My problem is that while the app appears to encrypt the data, I am unable to decrypt the data. The error message that is thrown is literally "unable to decrypt data" which is not helpful.

Server-side code for generating keypairs:

// Generate public/private keypairs
exports.generateKeyPair = (password) => {
    return new Promise((resolve, reject) => {
        crypto.generateKeyPair('rsa', {
            modulusLength: 4096,
            publicKeyEncoding: {
                type: 'spki',
                format: 'pem'
            },
            privateKeyEncoding: {
                type: 'pkcs8',
                format: 'pem',
                cipher: 'aes-256-cbc',
                passphrase: password
            }
        }, (err, publicKey, privateKey) => {
                if (err) reject(err);
                else resolve([publicKey, privateKey]);
        });
    })
}

Client-side code for decrypting and encrypting (Node crypto library is sent to client using Browserify):

var crypto = require('crypto');

window.encrypt = function (data, publicKey) {
    let buffer = Buffer.from(data);
    let encrypted = crypto.publicEncrypt(publicKey, buffer);
    return encrypted.toString('base64');
}

window.decrypt = function(data, privateKey, password) {
    let buffer = Buffer.from(data, 'base64');
    let decrypted = crypto.privateDecrypt({
        key: privateKey,
        passphrase: password
    }, buffer);
    return decrypted.toString('utf8');
}

Client-side code that interacts with the UI:

var sendMsg = function() {
    let token = $('#token').val();
    let toUser = $('#toUser').val();
    let message = btoa($('#sendMessage').val());
    fetch(`/keypairs/public/${toUser}?token=${token}`)
    .then((res) => res.json())
    .then((json) => {
        if (json.code != 200) throw 'Error';
        else return json.data.pubKey;
    })
    .then((pubKey) => encrypt(message, pubKey))
    .then((encrypted) => $('#send-result').html(encrypted))
    .catch((err) => alert(err));
};

var decryptMsg = function() {
    let token = $('#token').val();
    let encrypted = $('#decrypt-text').val();
    let password = $('#decrypt-pass').val();

    fetch(`/keypairs/private?token=${token}`)
    .then((res) => res.json())
    .then((json) => {
        if (json.code != 200) throw 'Error';
        else return json.data.privKey;
    })
    .then((privKey) => decrypt(encrypted, privKey, password))
    .then((decrypted) => $('#decrypt-result').html(decrypted))
    .catch((err) => (console.error(err), alert(err))); // <-- this line gives useless info
};

I paste the encrypted data into a field #'decrypt-text. I also pass the User B password. The token is retrieved during the sign-in process to associate the user with a key in the database. As I mentioned, the only error I get is "Unable to decrypt data". Any ideas? Perhaps I need to generate keys with pkcs1 type?

tycrek tycrek · Accepted Answer · 2019-09-24T16:29:56

I figured it out. This issue was that when I created the public keys, the types were spki and pkcs8. For some reason changing both to pkcs1 and regenerating the keys was able to fix it. I also tried passing type: 'pkcs8 to the decrypt function, but that did not work.

RSA private key unable to decrypt data

1 Answers