On the security of name-stamp protocols (Q1071729)

Protocols are of great importance to public key cryptography in order to prevent active saboteurs. Whereas in the construction of cascade protocols only encryption functions and decryption functions are used, additional types of functions occur in the construction of name stamp protocols: name appending functions, name matching functions and a deletion function. \textit{D. Dolev} and \textit{A. C. Yao} defined a notion of security of protocols [IEEE Trans. Inf. Theory IT-29, 198-208 (1983; Zbl 0502.94005)] and developed a characterization of two-party cascade protocols that are secure. In the present paper it is shown that there is no similar characterization of name stamp protocols that are secure.