Category Index:
/pub/doc/authentication Category Index:
/pub/doc/authentication
No Pointing!Aviel D. Rubin,
Trusted Distribution of Software over the Internet
Abstract: This paper offers a solution to a problem of
software distribution on the Internet. The problem is that
malicious software can be posted to the public with no
accountability. When this software is run, it inherits the
privileges of the user who runs it. Unfortunately, it is very
common for users to execute software obtained on the Internet
with no assurance that it is genuine. The solution offered here
utilizes a trusted third party that signs certificates to
identify the author of a program and to secure its integrity. A
detailed design is provided. Finally,Bellcore's Trusted Software
Integrity (Betsi) System, an implementation of the design, is
presented.
Derek A. Atkins,
Charon: Kerberos Extensions For Authentication Over Secondary
Networks
Abstract: This thesis describes extensions to the Kerberos
Authentication System to enable a secure method of Authentication
over multiple networks. Kerberos was designed with a
fully-connected IP network in mind, however when you add dialup
capabilities to the picture, Kerberos doesn't expand to secure
the whole connection. Charon was created to tackle this problem.
It was developed to provide a way to securely authenticate to a
login server over a modem connection, without allowing a passive
attacker to gain enough information to impersonate the user. This
means that a user can log into a Kerberized host without typing
his password in clear-text over the phone. In addition, no
modifications to the login server's base operating system need to
be made in order to accomplish this.
Liudvikas Bukys,
User Authentication Devices
Abstract: The document is a file with a summary of a
survey on currently available hand-held authentication devices
(as of March 9, 1994)
Michael Burrows, Martin Abadi, Roger Needham,
The Scope of a Logic of Authentication
Abstract: SRC Research Report 39 was originally published
on February 28, 1989, and revised on February 22, 1990. This is
an appendix to the revised version. The main body of the revised
version is available separately. (see SRC-039.ps)
Michael Burrows, Martin Abadi, Roger Needham,
A Logic of Authentication
Abstract: Questions of belief are essential in analyzing
protocols for the authentication of principals in distributed
computing systems. In this paper we motivate, set out, and
exemplify a logic specifically designed for this analysis; we
show how various protocols differ subtly with respect to the
required initial assumptions of the participants and their final
beliefs. Our formalism has enabled us to isolate and express
these differences with a precision that was not previously
possible. It has drawn attention to features of protocols of
which we and their authors were previously unaware, and allowed
us to suggest improvements to the protocols. The reasoning about
some protocols has been mechanically verified. This paper starts
with an informal account of the problem, goes on to explain the
formalism to be used, and gives examples of its application to
protocols from the literature, both with shared-key cryptography
and with public-key cryptography. Some of the examples are chosen
because of their practical importance, while others serve to
illustrate subtle points of the logic and to explain how we use
it. We discuss extensions of the logic motivated by actual
practice - for example, in order to account for the use of hash
functions in signatures. The final sections contain a formal
semantics of the logic and some conclusions.
M. Abadi, M. Burrows, C. Kaufman, B.
Lampson,
Authentication and Delegation with Smart-cards
Abstract: The authentication of users in distributed
systems poses special problems because users lack the ability to
encrypt and decrypt. The same problems arise when users wish to
delegate some of their authority to nodes, after mutual
authentication. In most systems today, the user is forced to
trust the node he wants to use. In a more satisfactory design,
the user carries a smart-card with sufficient computing power to
assist him; the card provides encryption and decryption
capabilities for authentication and delegation. Authentication is
relatively straightforward with a sufficiently powerful
smart-card. However, for practical reasons, protocols that place
few demands on smart-cards should be considered. These protocols
are subtle, as they rely on fairly complex trust relations
between the principals in the system (users, hosts, services). In
this paper, we discuss a range of public-key smart-card
protocols, and analyze their assumptions and the guarantees they
offer.
M. Abadi, M. Burrows, B.
Lampson, G. Plotkin,
A Calculus for Access Control in Distributed
Systems
Abstract: We study some of the concepts, protocols, and
algorithms for access control in distributed systems, from a
logical perspective. We account for how a principal may come to
believe that another principal is making a request, either on his
own or on someone else's behalf. We also provide a logical
language for access control lists, and theories for deciding
whether requests should be granted.
Butler
Lampson, Martin Abadi,
Michael Burrows, Edward Wobber,
Authentication in Distributed Systems: Theory and
Practice
Abstract: We describe a theory of authentication and a
system that implements it. Our theory is based on the notion of
principal and a "speaks for" relation between principals. A
simple principal either has a name or is a communication channel;
a compound principal can express an adopted role or delegation of
authority. The theory shows how to reason about a principal's
authority be deducing the other principals that it can speak for;
authenticating a channel is one important application. We use the
theory to explain many existing and proposed mechanisms for
security. In particular, we describe the system we have built. It
passes principals efficiently as arguments or results of remote
procedure calls, and it handles public and shared key encryption,
name lookup in a large name space, groups of principals, loading
programs, delegation, access control, and revocation.
Edward Wobber, Martin Abadi, Mike Burrows, and Butler Lampson,
Authentication in the Taos Operating System
Abstract: We describe a design for security in a
distributed system and its implementation. In our design,
applications gain access to security services through a narrow
interface. This interface provides a notion of identity that
includes simple principals, groups, roles, and delegations. A new
operating system component manages principals, credentials, and
secure channels. It checks credentials according to the formal
rules of a logic of authentication. Our implementation is
efficient enough to support a substantial user community.
Martin Abadi and Roger
Needham,
Prudent Engineering Practice for Cryptographic
Protocols
Abstract: We present principles for designing
cryptographic protocols. The principles are neither necessary nor
sufficient for correctness. They are however helpful, in that
adherence to them would have prevented a number of published
errors. Our principles are informal guidelines; they complement
formal methods, but do not assume them. In order to demonstrate
the actual applicability of these guidelines, we discuss some
instructive examples from the literature.
Steven M. Bellovin,
Security Problems in the TCP/IP Protocol Suite
Abstract: The TCP/IP protocol suite, which is very widely
used today, was developed under the sponsorship of the Department
of Defense. Despite that, there are a number of serious security
flaws inherent in the protocols, regardless of the correctness of
any implementations. We describe a variety of attacks based on
these flaws, including sequence number spoofing, routing attacks,
source address spoofing, and authentication attacks. We also
present defenses against these attacks, and conclude with a
discussion of broad-spectrum defenses such as encryption.
B. Clifford Neuman, Stuart G. Stubblebine,
A Note on the Use of Timestamps as Nonces
Abstract: The use of timestamps in key distribution
protocols was suggested by Denning and Sacco. Timestamps are now
used in most production authentication services including
Kerberos. Concerns have been raised about the security
implications of this practice. Timestamps are necessary in
authentication protocols that support multiple authentication
without multiple requests to an authentication server. Kehne,
Schonwalder, and Langendorfer have proposed a nonce-based
protocol for multiple authentications that they claim improves
upon the Kerberos protocol because it does not depend on the
presence of synchronized clocks. This note discusses the use of
timestamps as nonces and demonstrates a nonce-based
mutual-authentication protocol requiring only four messages, and
the same number of messages required for mutual-authentication in
Kerberos. The note concludes by suggesting extensions to our
protocol that allow the use of verifier issued timestamps as
nonces while recovering some (though not all) of the benefits of
traditional timestamps.
Bill Bryant,
Designing an Authentication System: a Dialogue in Four
Scenes
Abstract: This dialogue provides a fictitious account of
the design of an open-network authentication system called
"Charon." As the dialogue progresses, the characters Athena and
Euripides discover the problems of security inherent in an open
network environment. Each problem must be addressed in the design
of Charon, and the design evolves accordingly. Athena and
Euripides don't complete their work until the dialogue's close.
When they finish designing the system, Athena changes the
system's name to "Kerberos," the name, coincidentally enough, of
the authentication system that was designed and implemented at
MIT's Project Athena. The dialogue's "Kerberos" system bears a
striking resemblence to the system described in Kerberos: An
Authentication Service for Open Network Systems presented at the
Winter USENIX 1988, at Dallas, Texas.
Jennifer G. Steiner, Clifford Neuman, Jeffrey I. Schiller,
Kerberos: An Authentication Service for Open Network
Systems
Abstract: In an open network computing environment, a
workstation cannot be trusted to identify its users correctly to
network services. Kerberos provides an alternative approach
whereby a trusted third-party authentication service is used to
verify users' identities. This paper gives an overview of the
Kerberos authentication model as implemented for MIT's Project
Athena. It describes the protocols used by clients, servers, and
Kerberos to achieve authentication. It also describes the
management and replication of the database required. The views of
Kerberos as seen by the user, programmer, and administrator are
described. Finally, the role of Kerberos in the larger Athena
picture is given, along with a list of applications that
presently use Kerberos for user authentication. We describe the
addition of Kerberos authentication to the Sun Network File
System as a case study for integrating Kerberos with an existing
application.
Steven M. Bellovin, Michael Merritt,
Limitations Of The Kerberos Authentication System
Abstract: The Kerberos authentication system, a part of
MIT's Project Athena, has been has adopted by other
organizations. Despite Kerberos's many strengths, it has a number
of limitations and some weaknesses. Some are due to specifics of
the MIT environment; others represent deficiencies in the
protocol design. We discuss a number of such problems, and
present solutions to some of them. We also demonstrate how
special-purpose cryptographic hardware may be needed in some
cases.
Refik
Molva, Gene
Tsudik, Els
Van Herreweghen, Stefano
Zatti,
KryptoKnight Authentication and Key Distribution
System
Abstract: This paper describes KryptoKnight, an
authentication and key distribution system that provides
facilities for secure communication in any type of network
environment. KryptoKnight was designed with the goal of providing
network security services with a high degree of compactness and
flexibility. Message compactness of KryptoKnight's protocols
allows it to secure communication protocols at any layer, without
requiring any major protocol augmentations in order to
accommodate security-related information. Moreover, since
KryptoKnight avoids the use of bulk encryption it is easily
exportable. Owing to its architectural flexibility, KryptoKnight
functions at both endpoints of communication can perform
different security tasks depending on the particular network
configuration. These and other novel features make KryptoKnight
an attractive solution for providing security services to
existing applications irrespective of the protocol layer, network
configuration or communication paradigm.
Aviel Rubin, Peter Honeyman,
Long Running Jobs in an Authenticated Environment
Abstract: Current authentication systems require that a
user have a valid token or ticket for a job to run. These tickets
are issued with limited lifetimes, and their renewal requires a
user to enter her password. We have developed a system called lat
with which a user may schedule a batch job to be run at a later
date in the current environment. The batch job is stored on a
secure machine, and sent and received only in encrypted form.
When it is time for the job to run, the server generates a ticket
for the original user and sends it (encrypted) to the machine on
which the job will run. The user is given an option to specify
that tickets should be continually generated for the job until
its execution has completed.
David R. Safford, David K. Hess, Douglas Lee Schales, Secure
RPC Authentication (SRA) for TELNET and FTP
Abstract: TELNET and FTP currently exchange user
authentication (passwords) in plain text, which is easily
eavesdropped. Several techniques, such as Kerberos and SPX, have
been proposed in draft RFCs to implement secure authentication.
These techniques, however, have several drawbacks, including
technical complexity, poor vendor support, and organizational
problems. This paper presents SRA, a very simple and tested
technique based on Secure RPC which, while certainly not as
strong as RSA, is reasonably strong, fast, and trivial to
implement immediately for both inter and intra domain
communication.
Built by Mark Crosbie
and Ivan
Krsul.
Security Archive Homepage.
Purdue CS Dept page.
