Patent ID: 8520844

Claim:
A method for use in a device associated with a first party for decrypting a ciphertext according to a Cramer-Shoup based encryption scheme, the method comprising the steps of: obtaining the ciphertext in the first party device sent from a device associated with a second party; and generating in the first party device a plaintext corresponding to the ciphertext based on assistance from the second party device, wherein the assistance comprises an exchange of information between the first party device and the second party device separate from the sending of the ciphertext from the second party device to the first party device, the plaintext representing a result of the decryption according to the Cramer-Shoup based encryption scheme, such that the first party device and the second party device jointly perform a Cramer-Shoup based decryption operation of the ciphertext by each respectively performing one or more Cramer-Shoup based subcomputations of the joint Cramer-Shoup based decryption operation based at least in part on respective partial shares of a Cramer-Shoup based key that each party holds, but such that neither can decrypt the ciphertext alone.