In universal composability frameworks, adversaries (or environments) and protocols/ideal functionalities often have to exchange meta-information on the network interface, such as algorithms, keys, signatures, ciphertexts, signaling information, corruption-related messages. For these purely modeling-related messages, which do not reflect actual network communication, it would often be very reasonable and natural to expect that adversaries/environments provide the requested information immediately or give control back to the protocol/functionality immediately after having received some information. However, in none of the existing models for universal composability this is guaranteed. We call this the non-responsiveness problem. As discussed in the paper, while formally non-responsiveness does not invalidate any of the universal composability models, it has many disadvantages, such as unnecessarily complex specifications and less expressivity. Also, this problem has often been ignored ...
Jan Camenisch, Robert R. Enderlein, Stephan Krenn,