Encode a private key using a password

@param {string} privateKey - An hex private key
@param {string} password - A password

@return {object} - The encoded data
function(privateKey, password) {
    // Errors
    if (!privateKey || !password) throw new Error('Missing argument !');
    //if (!Helpers.isPrivateKeyValid(privateKey)) throw new Error('Private key is not valid !');
    // Processing
    let pass = derivePassSha(password, 20);
    let r = encrypt(privateKey, convert.hexToUint8(pass.priv));
    // Result
    return {
        ciphertext: CryptoJS.enc.Hex.stringify(r.ciphertext),
        iv: convert.uint8ToHex(r.iv)
    };
}