Els Van Herreweghen

KryptoKnight Authentication and Key Distribution System

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 KryptoKnights 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.

Non-repudiation in SET: Open Issues

The SET payment protocol uses digital signatures to authenticate messages and authorize transactions. It is assumed that these digital signatures make authorizations non-repudiable, i.e., provable to a third-party verifier. This paper evaluates what can be proved with the digital signatures in SET. The analysis shows that even a successful and completed SET protocol run does not give the ptlaties enough evidence to prove certain important transaction features. A comparison with the similarly-structured iKP protocol shows a number of advantages of iKP as opposed to SET with respect to the use of its signatures as evidence tokens. It is shown that non-repudiation requires more than digitally signing authorization messages. Most importantly, protocols claiming non-repudiaton should explicitly specify the rules to be used for deriving authorization statements from digitally signed messages.

On simple and secure key distribution

The encrypted key exchange (EKE) protocol is augmented so that hosts do not store cleartext passwords. Consequently, adversaries who obtain the one-way encrypted password file may (i) successfully mimic (spoof) the host to the user, and (ii) mount dictionary attacks against the encrypted passwords, but cannot mimic the user to the host. Moreover, the important security properties of EKE are preserved—an active network attacker obtains insufficient information to mount dictionary attacks. Two ways to accomplish this are shown, one using digital signatures and one that relies on a family of commutative one-way functions.

Some remarks on protecting weak keys and poorly-chosen secrets from guessing attacks

Authentication and key distribution protocols that utilize weak secrets (such as passwords and personal identification numbers) are traditionally susceptible to guessing attacks whereby an adversary iterates through a relatively small key space and verifies the correct guess. Such attacks can be defeated by the use of public key encryption and careful protocol construction. T. Lomas et al. (Proc. of ACM Symp. on Operating Syst. Principles, 1989) investigated this topic and developed a methodology for avoiding guessing attacks while incurring only moderate overhead. Several issues concerning the proposed solution are discussed here, and modifications that remove some of the constraints (such as synchronized time and state retention by the server) and result in simpler and more efficient protocols are suggested.<<ETX>>

Secure Anonymous Signature-Based Transactions

Electronic commerce protocols often require users to reveal their identities and other information not necessary for reasons of security. Some applications such as contract signing are often argued to require a signer’s authenticated identity; but this authentication may give the recipient a false feeling of security if certificate registration procedures do not guarantee a mapping to a liable person, or correctness of certificate data. In this paper, we propose a separation of identity from liability. Liability-aware certificates allow certificate issuers to make explicit which liabilities it takes with respect to the transaction, the certificate data or the signer’s identity. We illustrate their use in the design of a pseudonym service providing pseudonym certificates for secure anonymous transactions.

Robust and Secure Password and Key Change Method

This paper discusses issues and idiosyncrasies associated with changing passwords and keys in distributed computer systems. Current approaches are often complicated and fail to provide the desired level of security and fault tolerance. A novel and very simple approach to changing passwords/keys is presented and analyzed. It provides a means for human users and service programs to change passwords and keys in a robust and secure fashion.

Robust and secure password and key change method

This paper discusses issues and idiosyncrasies associated with changing passwords and keys in distributed computer systems. Current approaches are often complicated and fail to provide the desired level of security and fault tolerance. A novel and very simple approach to changing passwords/keys is presented and analyzed. It provides a means for human users and service programs to change passwords and keys in a robust and secure fashion.