Cryptographic protocols and methods of employing the same are described. The described protocols advantageously enable two or more identical encryptable objects that are coded for encryption with different keys to be identified as identical without access to either the unencrypted objects or the keys...http://www.google.de/patents/US7779253?utm_source=gb-gplus-sharePatent US7779253 - Encryption systems and methods for identifying and coalescing identical objects encrypted with different keys
