International Association
for Cryptologic Research

We present and implement schemes for authenticating messages from a

group of users to a recipient, with revocable anonymity and massive (very high) message rate. Our implementations present a trade-off between the efficiency and the security required: from online group managers that participate in every message sent to offline managers, from assuming a trusted group manager and a trusted recipient to securing against both entities. All implementations have the {\\em traceablity} feature, allowing to distributively and efficiently trace

all messages that originated from a specific group member without violating anonymity of other members. In addition, our schemes are efficient and practical.