I have a use case where I want to send an encrypted message to an account managed by metamask. I can already get the public key for a metamask account from a digital signature, so I can encrypt data with that. What I now need is a way to either access the private key directly (yikes) - or better yet - pass the encrypted data to metamask to be decrypted using the private key - perhaps with a confirmation dialog. I could of course solve this by creating my own key pair and managing it myself, but I would much prefer to piggyback on metamask infrastructure. Ideally this encryption api would be made a standard JS API so other account management systems (e.g. MIST/geth) could implement it too.