# Is there an additive homomorphic encryption that supports exponentation

For example say we have two numbers a and b. Now is there any partial homomorphic encryption scheme that allows to compute (a-b)^2 over the ciphertexts of a and b without round trips.

• Possible duplicate of Homomorphic Encryption with Addition and Exponentiation. Feb 17 '16 at 13:00
• I'm agreeing with mikeazo on this one. If you could compute $(a-b)^2$, you could also compute $ab=-(a-0)^2-(b-0)^2-(a-b)^2$ which would allow fully homomorphic encryption (assuming exponentiating with $1$ is allowed). The answer to the referenced question is lacking though, therefore I do not vote for closing as dupe.
– SEJPM
Feb 17 '16 at 20:55