Implementing Gentry's Fully-Homomorphic Encryption Scheme
Encryption schemes that support operations on encrypted data (aka homomorphic encryption) have a very wide range of applications in cryptography. This concept was introduced by Rivest et al. shortly after the discovery of public key cryptography, and many known public-key cryptosystems support either addition or multiplication of encrypted data. However, supporting both at the same time seems harder, and until very recently all the attempts at constructing so-called "Fully homomorphic" encryption turned out to be insecure.