Homomorphic encryption allows one to carry out operations on encrypted data without having to decrypt it; I could encrypt my data, send it to a big number-crunc

Homomorphic encryption allows one to carry out operations on encrypted data without having to decrypt it; I could encrypt my data, send it to a big number-crunching server, they do the operations without decrypting anything, and send it back to me to decrypt and see the results at my leisure. It's got some way to go, but it's certainly possible.