High Quality Content by WIKIPEDIA articles! The universal composability (UC) framework is a means for defining the security of cryptographic protocols. The name stems from the fact that instances of protocols that are UC secure remain secure even if arbitrarily composed with other instances of the same or other protocols. An ideal functionality is a protocol in which a trusted party that can communicate over perfectly secure channels with all protocol participants computes the desired protocol outcome. We say that a cryptographic protocol that cannot make use of such a trusted party fulfils an ideal functionality, if the protocol can emulate the behaviour of the trusted party for honest users, and if the view that an adversary learns by attacking the protocol is indistinguishable from what can be computed by a simulator that only interacts with the ideal functionality.