Is the cached data encrypted (Workers)?

I have tried to find information about it online but cannot seem to find any. Is the cached data encrypted?

Thanks in advance

From the feedback I got from Cloudflare staff the KVs are encrypted and I presume Cache API (beta) it is too.
You can also use the WebCrypto API to guarantee encryption on the worker.
Using WebCrypto API doesn’t add towards CPU time limits.

That is a good idea, I will do that thanks.

WebCrypto API actually does count towards CPU time limits, try doing a few rounds of tougher encryption and you’ll get a resource error.