TL;DR: It is shown that the group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves, and the average measured processing time per join/leave increases linearly with the logarithm of group size.
Abstract: Many emerging network applications are based upon a group communications model. As a result, securing group communications, i.e., providing confidentiality, authenticity, and integrity of messages delivered between group members, will become a critical networking issue. We present, in this paper, a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size.
TL;DR: A protocol for establishing the authenticity of a client to a server in an electronic transaction by encrypting a certificate with a key known only to the client and the server can be found in this article.
Abstract: A protocol for establishing the authenticity of a client to a server in an electronic transaction by encrypting a certificate with a key known only to the client and the server. The trust of the server, if necessary, can be established by a public key protocol. The client generates and sends over a communications channel a message containing at least a part of a certificate encrypted with the server's public key or a secret session key. The server receives and processes the message to recover at least part of the certificate, verifies and accepts it as proof of the client's authenticity.
TL;DR: PGP: Pretty Good Privacy by Simson Garfinkel is both a readable technical user's guide and a fascinating behind-the-scenes look at cryptography and privacy.
Abstract: From the Publisher:
Use of the Internet is expanding beyond anyone's expectations. As corporations, government offices, and ordinary citizens begin to rely on the information highway to conduct business, they are realizing how important it is to protect their communications -- both to keep them a secret from prying eyes and to ensure that they are not altered during transmission. Encryption, which until recently was an esoteric field of interest only to spies, the military, and a few academics, provides a mechanism for doing this.
PGP, which stands for Pretty Good Privacy, is a free and widely available encryption program that lets you protect files and electronic mail. Written by Phil Zimmermann and released in 1991, PGP works on virtually every platform and has become very popular both in the U.S. and abroad. Because it uses state-of-the-art public key cryptography, PGP can be used to authenticate messages, as well as keep them secret. With PGP, you can digitally "sign" a message when you send it. By checking the digital signature at the other end, the recipient can be sure that the message was not changed during transmission and that the message actually came from you.
PGP offers a popular alternative to U.S. government initiatives like the Clipper Chip because, unlike Clipper, it does not allow the government or any other outside agency access to your secret keys.
PGP: Pretty Good Privacy by Simson Garfinkel is both a readable technical user's guide and a fascinating behind-the-scenes look at cryptography and privacy. Part I, "PGP Overview," introduces PGP and the cryptography that underlies it. Part II, "Cryptography History and Policy," describes the history of PGP -- its personalities, legal battles, and other intrigues; it also provides background on the battles over public key cryptography patents and the U.S. government export restrictions, and other aspects of the ongoing public debates about privacy and free speech. Part III, "Using PGP," describes how to use PGP: protecting files and email, creating and using keys, signing messages, certifying and distributing keys, and using key servers. Part IV, "Appendices," describes how to obtain PGP from Internet sites, how to install it on PCs, UNIX systems, and the Macintosh, and other background information. The book also contains a glossary, a bibliography, and a handy reference card that summarizes all of the PGP commands, environment variables, and configuration variables.
TL;DR: In this article, the authors describe an automated management system for managing keys to encrypt and decrypt stored data on the computing system, which includes an authentication server, a key client, a generator, and an encrypted data file memory.
Abstract: A computing system is described having an automated management system for managing keys to encrypt and decrypt stored data on the computing system. The computing system has an authentication server; a key client; a key generator; a key server; a key database; and an encrypted data file memory. The authentication server authenticates the user and in response to the user accessing the computing system the authentication server provides the user with a ticket validating the user. The key client of a creating user when creating a data file invokes the generator to generate a key corresponding to the data file. The key is provided to the key server and the key client uses the key to encrypt the data file which is stored in the encrypted data file memory. The key client of an accessing user sends its ticket and data file identification data to the key server. The key server checks the ticket and sends the key corresponding to the data file to the key client of the accessing user. The key client of the accessing user uses the key to decrypt the encrypted data file. The stored data can further include a header containing the key and owner and permitted user identification data. The ticket can contain a key to encrypt messages sent between the client server and key client.
TL;DR: In this article, a secure document delivery over a wide area network, such as the Internet, is described, where a sender directs a Delivery Server to retrieve an intended recipient's public key.
Abstract: A method and system are provided for secure document delivery over a wide area network, such as the Internet. A sender directs a Delivery Server to retrieve an intended recipient's public key. The Delivery Server dynamically queries a certificate authority and retrieves the public key. The public key is transmitted from the Delivery Server to the sender. The sender encrypts the document using a secret key and then encrypts the secret key using the public key. Both encrypted document and encrypted secret key are uploaded to the Delivery Server, and transmitted to the intended recipient. The intended recipient then uses the private key associated with the public key to decrypt the secret key, and uses the secret key to decrypt the document. In an alternative, equally preferred embodiment of the invention, the sender uses the public key to encrypt the document. In yet another embodiment, the server transmits the document to the Delivery Server for encryption.