We have a NativeScript Android application that gets files from the cloud into the document directory. We would like to encrypt the files in the document directory.

So far we looked at crypto-js but I could not find how to encrypt binary contents, only UTF-8 or base64.

So we tried the basic thing of converting our file to base64 and saving this (before adding the real encryption) even this did not work.

Note that each file is about 1Mb in size, the files are epub files which are basically zip files.

So we need a simple method of encrypting a binary file. We also tried using native-script-secure-storage but it works only on small strings.