cms: Encrypt, Decrypt, or Verify Functions

[dhouck]

This is either a feature request or a documentation request.

Looking through the documentation, I can see how I could sign a message using the cms crate, using the cms::builder::SignedDataBuilder class. I donʼt see how to encrypt or decrypt data, or how to verify the signatures created here.

Am I just missing something obvious, or are these not supported? Based on the repo name I would assume it was intended to be just the types, but signing is it looks like other operations are also supported for other formats. If I am looking at the wrong repository, could you direct me to the right RustCrypto project for this, if there is one, and include that in the docs?

[tarcieri]

See #1115

[dhouck]

That looks useful for encryption but not for verification/decryption, if Iʼm reading it right? Which is useful, although unfortunately the part I personally most want is signature verification.