Node aes-gcm-stream and Web Crypto API

node_aes_gcm_stream_base64.js

var aesgcm = require('aes-gcm-stream');
var fs = require('fs');


var encryptToB64 = function (config, message) {
    return new Promise(function (resolve, reject) {
        var encrypt = aesgcm.encrypt(config);
        var buffer = [];
        encrypt.on('data', function (chunk) {
            buffer.push(chunk);
        });

        var eData;
        encrypt.on('end', function () {
            eData = Buffer.concat(buffer);
            resolve(eData.toString('base64'));
        });

        encrypt.write(message);
        encrypt.end();
    });
};

// Wait

var decryptFromB64 = function (config, encryptedMessage) {
    return new Promise(function (resolve, reject) {
        var eData = Buffer.from(encryptedMessage, 'base64');
        var decrypt = aesgcm.decrypt(config);
        var dData;
        var buffer = [];
        decrypt.on('data', function (chunk) {
            buffer.push(chunk);
        });
        decrypt.on('end', function () {
            resolve(Buffer.concat(buffer));
        });

        decrypt.write(eData);
        decrypt.end();
    });
};

var config = {key: aesgcm.createKeyBuffer()};
console.log('key:', config.key.toString('base64'));
var eMsg = encryptToB64(config, 'Hello World').then(function (eMsg) {
    console.log('eMsg:', eMsg);
    return decryptFromB64(config, eMsg);
}).then(function (msgBuffer) {
    console.log('decrypted: ', msgBuffer.toString());
});

web_crypto_decrypt_node_aes_gcm_stream.js

//Example of decoding base64 string encrypted with node aes-gcm-stream using webcrypto

var b64ToArray = function (base64Data, cb) {
    var promise = new Promise(function(resolve, reject) {
        var req = new XMLHttpRequest;
        req.open('GET', "data:application/octet;base64," + base64Data);
        req.responseType = 'arraybuffer';
        req.onload = function fileLoaded(e) {
            var byteArray = new Int8Array(e.target.response);
            resolve(byteArray);
        }
        req.send();
    });
    return promise;
}

var makeImportKey = function (b64key, cb) {
    return b64ToArray(b64key).then(function (keyArray) {
        return window.crypto.subtle.importKey(
            "raw",
            keyArray,
            {
                name: "AES-GCM",
            }
            ,
            false,
            ["encrypt", "decrypt"]
        );
    });
}

var decrypt = function (b64Key, b64msg, cb) {
    var key;
    return makeImportKey(b64Key).then(
        function (k) {
            key = k;
            return b64ToArray(b64msg);
        }
    ).then(
        function (dataArray) {
            iv = dataArray.slice(0, 12);
            dataArray = dataArray.slice(12);
            return window.crypto.subtle.decrypt(
                {
                    name: "AES-GCM",
                    iv: iv,
                },
                key,
                dataArray
            );
        }
    );
}

//Strings from aes-gcm-stream, see node_aes_gcm_stream_base64.js
var b64key = 'RU8FrL/KxRsOEKZ6a/zZLgpF8Cq8s9Ud4fR4rdnzpCw=';
var eDataB64 = '8Ldk+zjB6OSr7d72EpQTtsQCKCABI+eA2hjEq8Dhz+o4usB1BNBf';

decrypt(b64key, eDataB64).then(function (dd) {
    console.log(String.fromCharCode.apply(null, new Uint8Array(dd)));
}).catch(function(err) { console.log(err); });