[Cryptography] composing EC & RSA encryption?

[Jerry Leichter]

> ...An EC/RSA signing form is easy - just make one signature in RSA and one in EC, and we're done.  At least at a trivial level, this works, although I imagine it might be possible to do better - interesting work for a grad student perhaps.
> 
> But what about encryption?  Doing that in parallel makes it weaker, it would have to be done in serial....
Not sure what you're getting at.  The only thing you want to encrypt with a public key is a key for an asymmetric cipher.  Generate two random values, encrypt one with EC, one with RSA; use the XOR of the two as your actual asymmetric key.  As strong as the stronger of the two.

Same goes for key agreement.
                                                        -- Jerry