Proxy re-encryption: Difference between revisions

Revision as of 00:47, 13 October 2013

Revision as of 00:57, 22 July 2014

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{{no footnotes|date=October 2013}}

'''Proxy re-encryption''' schemes are [[cryptosystems]] which allow third- parties ([[proxy server|proxies]]) to alter a [[ciphertext]] which has been [[encryption|encrypted]] for one party, so that it may be decrypted by another.

==Examples of Useuse==

{{Expert-subject|Cryptography|section|date=June 2007}}

Bob could designate a proxy to re-encrypt one of his messages that is to be sent to Chris. This generates a new [[Key (cryptography)|key]] that Chris can use to decrypt the message. Now if Alice sends Chris a message that was encrypted under Bob's key, the proxy will alter the message, allowing Chris to decrypt it. This method allows for a number of applications such as [[e-mail forwarding]], law-enforcement monitoring, and content distribution.

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A weaker re-encryption scheme is one in which the proxy possesses both parties' keys simultaneously. One key decrypts a [[plaintext]], while the other encrypts it. Since the goal of many proxy re-encryption schemes is to avoid revealing either of the keys or the underlying plaintext to the proxy, this method is not ideal.

==Defining Functionsfunctions==

Proxy re-encryption schemes are similar to traditional [[symmetric]] or [[Public-key cryptography|asymmetric encryption]] schemes, with the addition of two functions:

* '''Delegation''' - allows a message recipient (keyholder) to generate a re-encryption key based on his secret key and the key of the delegated user. This re-encryption key is used by the proxy as input to the re-encryption function, which is executed by the proxy to translate ciphertexts to the delegated user's key. Asymmetric proxy re-encryption schemes come in bi-directional and uni-directional varieties.