OpenPGP, an IETF Proposed Standard based on PGP application, has its own Public Key Infrastructure (PKI) architecture which is different from the one based on X.509, another standard from ITU. This paper describes the OpenPGP PKI; the historical perspective as well as its current use. The current OpenPGP PKI issues include the capability of a PGP keyserver and its performance. PGP keyservers have been developed and operated by volunteers since the 1990s. The keyservers distribute, merge, and expire the OpenPGP public keys. Major keyserver managers from several countries have built the globally distributed network of PGP keyservers. However, the current PGP Public Keyserver (pksd) has some limitations. It does not support fully the OpenPGP format so that it is neither expandable nor flexible, without any cluster technology. Finally we introduce the project on the next generation OpenPGP public keyserver called the OpenPKSD, lead by Hironobu Suzuki, one of the authors, and funded by Japanese Information-technology Promotion Agency(IPA).
A web of trust'' used in PGP is referred in several researches including the peer-to-peer authentication @cite_9 , trust computation @cite_7 @cite_14 , and privacy enhanced technology @cite_6 . However, there are few description on PGP keyserver. It might be because PGP keyserver mechanism is too simple. It is not a CA but just a pool of public keys. From users' viewpoint, PGP keyserver has a large amount of OpenPGP public keys that provide the interesting material for social analysis of network community. For example, OpenPGP keyserver developer Jonathan McDowell also developed Experimental PGP key path finder'' @cite_20 that searches and displays the chain of certification between the users.
@cite_14 @cite_7 @cite_9 @cite_6 @cite_20
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PGP is built upon a Distributed Web of Trust in which a user’s trustworthiness is established by others who can vouch through a digital signature for that user’s identity. Preventing its wholesale adoption are a number of inherent weaknesses to include (but not limited to) the following: 1) Trust Relationships are built on a subjective honor system, 2) Only first degree relationships can be fully trusted, 3) Levels of trust are difficult to quantify with actual values, and 4) Issues with the Web of Trust itself (Certification and Endorsement). Although the security that PGP provides is proven to be reliable, it has largely failed to garner large scale adoption. In this paper, we propose several novel contributions to address the aforementioned issues with PGP and associated Web of Trust. To address the subjectivity of the Web of Trust, we provide a new certificate format based on Bitcoin which allows a user to verify a PGP certificate using Bitcoin identity-verification transactions - forming first degree trust relationships that are tied to actual values (i.e., number of Bitcoins transferred during transaction). Secondly, we present the design of a novel Distributed PGP key server that leverages the Bitcoin transaction blockchain to store and retrieve our certificates. 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. Authentication using a path of trusted intermediaries, each able to authenticate the next in the path, is a well-known technique for authenticating channels in a large distributed system. In this paper, we explore the use of multiple paths to redundantly authenticate a channel and focus on two notions of path independence-disjoint paths and connective paths-that seem to increase assurance in the authentication. We give evidence that there are no efficient algorithms for locating maximum sets of paths with these independence properties and propose several approximation algorithms for these problems. We also describe a service we have deployed, called PathServer, that makes use of our algorithms to find such sets of paths to support authentication in PGP applications. The Public Key Infrastructure (PKI) in use today on the Internet to secure communications has several drawbacks arising from its centralised and non-transparent design. In the past there has been instances of certificate authorities publishing rogue certificates for targeted attacks, and this has been difficult to immediately detect as certificate authorities are not transparent about the certificates they issue. Furthermore, the centralised selection of trusted certificate authorities by operating system and browser vendors means that it is not practical to untrust certificate authorities that have issued rogue certificates, as this would disrupt the TLS process for many other hosts. SCPKI is an alternative PKI system based on a decentralised and transparent design using a web-of-trust model and a smart contract on the Ethereum blockchain, to make it easily possible for rogue certificates to be detected when they are published. The web-of-trust model is designed such that an entity or authority in the system can verify (or vouch for) fine-grained attributes of another entity's identity (such as company name or domain name), as an alternative to the centralised certificate authority identity verification model.