This paper proposes a new and efficient two-pass protocol for authenticated key agreement in the asymmetric (public-key) setting. The protocol is based on Diffie-Hellman key agreement and can be modified to work in an arbitrary finite group and, in particular, elliptic curve groups. Two modifications of this protocol are also presented: a one-pass authenticated key agreement protocol suitable for environments where only one entity is on-line, and a three-pass protocol in which key confirmation is additionally provided. The protocols are currently under consideration for standardization in ANSI X9.42 [2], ANSI X9.63 [4] and IEEE P1363 [18]. Keywords: Diffie-Hellman, authenticated key agreement, key confirmation, elliptic curves. An Efficient Protocol for Authenticated Key Agreement 1 1 Introduction Key establishment is the process by which two (or more) entities establish a shared secret key. The key is subsequently used to achieve some cryptographic goal such as confidentiality or d...

Many modern computing environments involve dynamic peer groups. Distributed simulation, multi-user games, conferencing and replicated servers are just a few examples. Given the openness of today's networks, communication among group members must be secure and, at the same time, efficient. This paper studies the problem of authenticated key agreement in dynamic peer groups with the emphasis on efficient and provably secure key authentication, key confirmation and integrity. It begins by considering 2-party authenticated key agreement and extends the results to Group Diffie-Hellman key agreement. In the process, some new security properties (unique to groups) are discussed. 1 Introduction This paper is concerned with security services in the context of dynamic peer groups (DPGs). Such groups are common in many network protocol layers and in many areas of modern computing and the solution to their security needs, in particular key management, are still open research challenges [19]. Exa...

Consider the well-known oracle attack: Somehow one gets a certain computation result as a function of a secret key from the secret key owner and tries to extract some information on the secret key. This attacking scenario is well understood in the cryptographic community. However, there are many protocols based on the discrete logarithm problem that turn out to leak many of the secret key bits from this oracle attack, unless suitable checkings are carried out. In this paper we present a key recovery attack on various discrete log-based schemes working in a prime order subgroup. Our attack can disclose part of, or the whole secret key in most Diffie-Hellman-type key exchange protocols and some applications of ElGamal encryption and signature schemes. Key Words : Key recovery attack, Discrete logarithms, Key exchange, Digital signatures. 1 Introduction Many cryptographic protocols have been developed based on the discrete logarithm problem. The main objective of developers is to design...

This paper describes a new public-key cryptosystem where the ciphertext is obtained by multiplying the public-keys indexed by the message bits and the cleartext is recovered by factoring the ciphertext raised to a secret power.

Abstract. A number of signature schemes and standards have been recently designed, based on the Discrete Logarithm problem. In this paper we conduct design validation of such schemes while trying to minimize the use of ideal hash functions. We consider several Discrete Logarithm (DSA-like) signatures abstracted as generic schemes. We show that the following holds: “if the schemes can be broken by an existential forgery using an adaptively chosen-message attack then either the discrete logarithm problem can be solved, or some hash function can be distinguished from an ideal one, or multicollisions can be found. ” Thus, for these signature schemes, either they are equivalent to the discrete logarithm problem or there is an attack that takes advantage of properties which are not desired (or expected) in strong practical hash functions (SHA-1 or whichever high quality cryptographic hash function is used). What is interesting is that the schemes we discuss include KCDSA and slight variations of DSA. Further, since our schemes coincide with (or are extremely close to) their standard counterparts they benefit from their desired properties: efficiency of computation/space, employment of certain mathematical operations and wide applicability to various algebraic

We present an attack on plain ElGamal and plain RSA encryption. The attack shows that without proper preprocessing of the plaintexts, both ElGamal and RSA encryption are fundamentally insecure. Namely, when one uses these systems to encrypt a (short) secret key of a symmetric cipher it is often possible to recover the secret key from the ciphertext. Our results demonstrate that preprocessing messages prior to encryption is an essential part of both systems.

We present a new secure authenticated group key exchange algorithm for large groups. The protocol

This paper describes a new type of attack on tamper-resistant cryptographic hardware. We show that by locally observing the value of a few RAM or adress bus bits (possibly a single one) during the execution of a cryptographic algorithm, typically by the mean of a probe (needle), an attacker could easily recover information on the secret key being used; our attacks apply to public-key cryptosystems such as RSA or El Gamal, as well as to secret-key encryption schemes including DES and RC5.

Formal analysis techniques have proved successful in finding flaws in security protocols. Such techniques typically assume the presence of perfect encryption, an assumption that is clearly not true in practice. When we aim to prove the correctness of a protocol, we must be more careful in assuming bounds on the capabilities of the intruder: a real intruder can, and will, exploit properties of the underlying cryptosystem. The Diffie-Hellman key agreement scheme exhibits a rich set of algebraic properties, and this report suggests how the existing CSP approach can be extended to incorporate these properties in a rank function verification. The utility of the approach is established by performing an analysis of a key agreement protocol from the CLIQUES suite.

Abstract not found