Bdtjtk

I want to rebuild a symmetric encryption I am using from an angular library in my android app to decrypt messages.

Those are the functions of the angular library (https://www.npmjs.com/package/angular-encryption-service):

EncryptionService.prototype.generateKey = function (passphrase) {

        return this.config.getSalt().then(function (salt) {

            var /** @type {?} */ passphraseBytes = new textEncodingUtf8.TextEncoder().encode(passphrase);

            var /** @type {?} */ importedKeyPromise = window.crypto.subtle.importKey('raw', passphraseBytes, { 'name': 'PBKDF2' }, false, ['deriveKey']);

            var /** @type {?} */ derivedKeyPromise = importedKeyPromise.then(function (key) {

                return window.crypto.subtle.deriveKey({

                    'name': 'PBKDF2',

                    'salt': typescriptBase64Arraybuffer.decode(salt),

                    // This should take around 0.5s to 1s

                    'iterations': 1000000,

                    'hash': 'SHA-256'

                }, key, { 'name': 'AES-CBC', 'length': 256 }, false, ['encrypt', 'decrypt']);

            });

            return derivedKeyPromise;

        });

    };

    /**

     * @param {?} text

     * @param {?} key

     * @return {?}

     */

    EncryptionService.prototype.encrypt = function (text, key) {

        var /** @type {?} */ iv = new Uint8Array(16);

        window.crypto.getRandomValues(iv);

        return (window.crypto.subtle.encrypt({ 'name': 'AES-CBC', 'iv': iv }, key, new textEncodingUtf8.TextEncoder().encode(text)).then(function (cipherBuffer) {

            // Need to implement base64 stuff here:

            return typescriptBase64Arraybuffer.encode(iv.buffer) + ':' + typescriptBase64Arraybuffer.encode(cipherBuffer);

        }));

    };

    /**

     * @param {?} cipherText

     * @param {?} key

     * @return {?}

     */

    EncryptionService.prototype.decrypt = function (cipherText, key) {

        try {

            var /** @type {?} */ pieces = cipherText.split(':');

            if (pieces.length !== 2) {

                return Promise.reject(new Error('encrypted text not formatted properly; missing ":"'));

            }

            var /** @type {?} */ iv = typescriptBase64Arraybuffer.decode(pieces[0]);

            var /** @type {?} */ buffer = typescriptBase64Arraybuffer.decode(pieces[1]);

            return (window.crypto.subtle.decrypt({ 'name': 'AES-CBC', 'iv': iv }, key, buffer).then(function (decryptedBuffer) {

                return new textEncodingUtf8.TextDecoder().decode(new Uint8Array(decryptedBuffer));

            }));

        }

        catch (e) {

            return Promise.reject(e);

        }

    };

I stumbled across this answer:
PBKDF2 with SHA256 on android

However the 1000000 iterations are not viable to perform on my phone (app dies after like a minute).

So I have two choices - either switch the angular library or find a way to do this in android. Which would be the best way to do this?