“…In the literature we also often see cryptosystems and cryptographic protocols (crypto schemes) that make use of prime order subgroups of Z * n (e.g., [1,2,8,9,11,13]). In the sequel, whenever we say subgroup, we refer to a prime order subgroup of Z We will analyze each of the crypto schemes referred in the above paragraph and itemize three classes of security failures from our analysis.…”