Proxy Re-Encryption and Re-Signatures from Lattices
Proxy re-encryption (PRE) and Proxy re-signature (PRS) were introduced by Blaze, Bleumer and Strauss [Eurocrypt ’98]. Basically, PRE allows a semi-trusted proxy to transform a ciphertext encrypted under one key into an encryption of the same plaintext under another key, without revealing the underlying plaintext. Since then, many interesting applications have been explored, and constructions in various settings have been proposed. On the other hand, PRS allows a semi-trusted proxy to transform Alice’s signature on a message into Bob’s signature on the same message, but the proxy cannot produce new valid signature on new messages for either Alice or Bob.