As of this writing Apple’s Safari browser still provides the Web Cryptography API via a prefixed name. Instead of using window.crypto.subtle you would use window.crypto.webkitSubtle. Even though it’s prefixed, it appears very compatible with the latest draft. So here’s a code snippet you can add to make working with both Apple and non-Apple browsers easier:
if (window.crypto && !window.crypto.subtle && window.crypto.webkitSubtle) {
window.crypto.subtle = window.crypto.webkitSubtle;
}
Normally, window.crypto.subtle is a read-only property and assigning to it does nothing. That’s a security aid in case some malicious code gets into your browser and tries to replace the real API with a compromised one. But since that property doesn’t exist on current versions of Safari, the assignment works, and from that point on you can use window.crypto.subtle.
However, even with that patch, most of the examples so far in this blog still won’t work because they rely on Blobs and Blob URLs to download files, and Safari’s support of that is broken. Or maybe Safari is right and every other browser is wrong. That seems to be the subtext of this bug report. You can always modify the examples to send the files to a remote server or use data URLs instead.
Charles Engelke's Blog 