Abstract: A selective broadcasting method operative to transmit a plurality of message data signals to a corresponding plurality of subscriber subsets within a set of subscribers, the method comprising receiving an indication of a privileged set comprising an individual subset and transmitting a message data signal from which a key can be extracted by members of the privileged set and cannot be extracted by any set of members outside the privileged set whose number of members is less than a predetermined resiliency, wherein the length of the message data signal is less than the sum of lengths of the message data signals required if an individual message data signal is transmitted to each subscriber in the privileged set.

Abstract: A computation for batch processing public key encryption method using a processor. The method batch processes an e1.sup.th root of a first message-data signal, M1, as M1.sup.1/e1, and an e2.sup.th root of a second message-data signal, M2,. where e1 and e2 are relatively prime, using the steps of computing an exponent product, e, by multiplying e1 times e2; computing a message product, M, wherein M=M1 .sup.(e/e1) M2.sup.(e/e2) ; computing a batch root, R, wherein R=M.sup.1/e ; computing the euclidean inverse, t, of e2 modulo e1; and computing R.sup.e2*t /(M1.sup.(e2*t-1)/e1 M2.sup.t), thereby generating M1 .sup.(1/e1). For a plurality of message-data signals, the method batch processes a plurality of message-data-signal roots as the e1, e2, . . ., ek, roots for a plurality of message-data signals, M1, M2, . . . Mk, respectively, where the ei and ej are pairwise relatively prime for i.noteq.j.

Abstract: A method and apparatus for simple identification and signature which enable any user to prove his identity and the authenticity of his messages to any other user. The method and apparatus are provably secure against any known or chosen message attack if factoring is difficult, and require only 1% to 4% of the number of modular multiplications previously required. The simplicity, security and speed of the method and apparatus derive from microprocessor-based devices which may be incorporated into smart cards, personal computers, passports, and remote control systems.