Show HN: Password-protect a file with Easy Encryption Everywhere

My friend needed to send credit-card data to a client and couldn't find a widely available program for sending password-protected files. So, I wrote one. This webpage encrypts a file and packages it into an HTML file, which contains JavaScript code to accept a password and decrypt the data. The code uses the Web Cryptography API and works with every major browser released since 2015.

I'd love feedback. Especially from experts on cryptography and the Web Cryptography API.