Microsoft SEAL
Easy-to-use and powerful homomorphic encryption library
...Developed by the Cryptography and Privacy Research group at Microsoft, it enables software engineers to build end-to-end encrypted data storage and computation services that never have to procure the customer's key. Microsoft SEAL is very easy to use, compile and run in many different environments.
Homomorphic encryption is an encryption scheme that allows the cloud to compute directly on the encrypted data, without requiring the data to be decrypted first. This results in encrypted computations remaining encrypted, decrypted only by the data owner using the secret key.