ABSTRACTProxy re‐encryption (PRE) is a public key encryption that allows a semi‐trusted proxy with some information (a.k.a., re‐encryption key) to transform a ciphertext under one public key into another ciphertext under another public key. Because of this special property, PRE has many applications, such as the distributed file system. Some of these applications demand that the underlying PRE scheme is anonymous under chosen‐ciphertext attacks (CCAs); that is, the adversary cannot identify the recipient of the original/transformed ciphertext, even if it knows the PRE key and can launch the CCA. However, to the best of our knowledge, none of the existing PRE schemes satisfy this requirement. In this work, we propose the first anonymous PRE with CCA security and collusion resistance. Our proposal is proved in the random oracle model based on the DDH assumption. Copyright © 2011 John Wiley & Sons, Ltd.