How do I create a cypher using a Bitcoin public key?

[Elwar]

I need to create a cypher of some data and I would like to use a Bitcoin public key to encrypt it with its corresponding private key to decrypt it.

I am doing this in Java and looking at the Cypher class I see RSA and other keys but I doubt they can be used with Bitcoin addresses.

Is there an easy way to do this or some sample java code I could use?

Am I correct in the belief that creating a cypher of data with a public key is different from the bitcoin client's creation of signing a message?