Syntax Notation One (ASN.1), CCITT Recommendation X.208 (ISO 8824, ISO 8824/AD1), Blue Book Vol. VIII, Fascicle VIII.4, Geneva, 1989 [X.209] Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1), CCITT Recommendation X.208 (ISO 8825, ISO 8825/AD1), Blue Book Vol. VIII, Fascicle VIII.4, Geneva, 1989 [X.210] Layer Service Definition Conventions, CCITT Recommendation X.210 (ISO TR 8509), Blue Book Vol. VIII, Fascicle VIII.4, Geneva, 1989 [X.213] Network Service Definition for Open Systems Interconnection for CCITT Applications, CCITT Recommendation X.213 (ISO 8348, ISO 8348/AD2, ISO 8348/AD3), Blue Book Vol. VIII, Fascicle VIII.4, Geneva, 1989 [X.217] Association Control Service Definition for Open Systems Interconnection for CCITT Applications, CCITT Recommendation X.217 (ISO 8649), Blue Book Vol. VIII, Fascicle VIII.4, Geneva, 1989 [X.218] Reliable Transfer: Model and Service Definition, CCITT Recommendation X.218 (ISO 9066-1), Blue Book Vol. VIII, Fascicle VIII...

We present some practical security protocols that use private-key encryption in the public-key style. Our system combines a new notion of private-key certificates, a simple key-translation protocol, and key-distribution. These certificates can be administered and used much as public-key certificates are, so that users can communicate securely while sharing neither an encryption key nor a network connection. Suppose as usual that Alice and Bob want to communicate securely. Conventional private-key authentication requires that they share a secret key, but if instead each shares a key with a translator Tom, Alice and Bob can avoid sharing directly by using Tom as an intermediary [9, 11, 5, 2]. Bob writes a message for Alice, but encrypts it for Tom's eyes only; when Alice wants to read this message, she asks Tom to translate its encryption into her key. Tom is trusted not only to keep the message secret, but also to sign the message as Bob's proxy: 1. B 0! A : fA, msggK b;t 2. A 0! T : ...

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Dispute of transactions is a common problem that could jeopardise business. Hence non-repudiation services are essential in business transactions which provide evidence to enable dispute resolution. To be eligible as non-repudiation evidence, the digital signature on an electronic document should remain valid until its expiry date which is specified by some non-repudiation policy. The conventional approaches are either inefficient or insecure to achieve non-repudiation in electronic commerce. This article presents a practical scheme

Linköpings tekniska högskola

The literature of cryptography has a curious history. Secrecy, of course, has always played a central role, but until the First World War, important developments appeared in print in a more or less timely fashion and the field moved forward in much the same way as other specialized disciplines. As late as 1918, one of the most influential cryptanalytic papers of the twentieth century, William F. Friedman’s monograph The Index of Coincidence and Its Applications in Cryptography, appeared as a research report of the private Riverbank Laboratories [577]. And this, despite the fact that the work had been done as part of the war effort. In the same year Edward H. Hebern of Oakland, California filed the first patent for a rotor machine [710], the device destined to be a mainstay of military cryptography for nearly 50 years. After the First World War, however, things began to change. U.S. Army and Navy organizations, working entirely in secret, began to make fundamental advances in cryptography. During the thirties and forties a few basic papers did appear in the open literature and several treatises on the subject were published, but the latter were farther and farther behind the state of the art. By the end of the war the transition was complete. With one notable exception, the public literature had died. That exception was Claude Shannon’s paper “The Communication Theory of Secrecy Systems, ” which