function stringToArrayBuffer(str) {
    var buf = new ArrayBuffer(str.length);
    var bufView = new Uint8Array(buf);
    for (var i = 0, strLen = str.length; i < strLen; i++) {
        bufView[i] = str.charCodeAt(i);
    }
    return buf;
}


function arrayBufferToString(str) {
    var byteArray = new Uint8Array(str);
    var byteString = '';
    for (var i = 0; i < byteArray.byteLength; i++) {
        byteString += String.fromCodePoint(byteArray[i]);
    }
    return byteString;
}


function encryptWithKey(key, data) {
    // Encrypt data with key. Return a Promise
    return new Promise((resolve) => {
        window.crypto.subtle.encrypt(
            {
                name: "AES-GCM",
                iv: stringToArrayBuffer(key.uuid),
            },
            key.key,
            stringToArrayBuffer(data)
        ).then(text => {

            resolve(btoa(arrayBufferToString(text)));

        });
    });
}


function decryptWithKey(key, data) {
    // Decrypt data with key. Return a Promise
    return new Promise((resolve) => {
        window.crypto.subtle.decrypt(
            {
                name: "AES-GCM",
                iv: stringToArrayBuffer(key.uuid),
            },
            key.key,
            stringToArrayBuffer(atob(data))
        ).then(text => {

            resolve(arrayBufferToString(text));

        });
    })
}