tangoDecrypt.js

var forge = require("node-forge");

function trimZeroes(data) {
	return data.toString().replace(/^\0+/, "").replace(/\0+$/, "");
}

function tangoDecrypt(tangoHash, tangoSharedSecret) {
	var decodedKey = new Buffer(tangoSharedSecret, "base64");
	var ivSize = decodedKey.length;

	var decodedHash = new Buffer(tangoHash.trim(), "base64");
	var iv = forge.util.createBuffer(decodedHash.slice(0, ivSize).toString("binary"));
	var data = forge.util.createBuffer(decodedHash.slice(ivSize).toString("binary"));

	var decipher = forge.cipher.createDecipher("AES-CBC", decodedKey.toString("binary"));
	decipher.start({
		iv: iv
	});
	decipher.update(data);
	decipher.finish();

	return JSON.parse(trimZeroes(decipher.output));
}

module.exports = tangoDecrypt;