Cryptanalysis of the Secure Sessions from Weak Secrets Protocols

The Short Secret Sharing Protocols (S3P), proposed by Roe et al in 1998 [13] and revised in 2003 [14], is a family of protocols that bootstrap secure session keys from weak secrets such as passwords. In this letter, we describe an attack against the RSA variants of the S3P protocols. The attacker can successfully masquerade as one of the participants, establish a new session, and gain knowledge of the session key. We present possible modifications to the protocol to prevent such an attack.