We explore authenticated group key agreement in data-sharing Peer-to-Peer networks. We first propose a novel password-based authenticated group key agreement protocol with key confirmation. We present a formal statement of its security in a variant of the Bresson et al. security model adapted for the password-based setting. A discussion of the limitations of our protocol in the case where the group size becomes large is then presented. We conclude the paper with an enhanced version of the protocol, using a CAPTCHA technique, designed to make it more robust against online password guessing attacks.
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