Attacks on improved key distribution protocols with perfect reparability

In this paper, we present attacks on two improved key distribution protocol with perfect reparability that were presented at ICON 2000. First, we show that the two ldquoattacksrdquo described in their paper are trivial and do not count as attacks at all since they are well-known attacks that apply to any security system. Further, we describe several attacks on both improved protocols, and show that an illegitimate attacker could easily impersonate legitimate parties and have other parties think they are sharing keys with the impersonated party when in fact that party is not present at all

Statically detecting message confusions in a multi-protocol setting

In a multi-protocol setting, different protocols are concurrently executed, and each principal can participate in more than one. The possibilities of attacks therefore increase, often due to the presence of similar patterns in messages. Messages coming from one protocol can be confused with similar messages coming from another protocol. As a consequence, data of one type may be interpreted as data of another, and it is also possible that the type is the expected one, but the message is addressed to another protocol. In this paper, we shall present an extension of the LySa calculus [7, 4] that decorates encryption with tags including the protocol identifier, the protocol step identifier and the intended types of the encrypted terms. The additional information allows us to find the messages that can be confused and therefore to have hints to reconstruct the attack. We extend accordingly the standard static Control Flow Analysis for LySa, which over-approximates all the possible behaviour of the studied protocols, included the possible message confusions that may occur at run-time. Our analysis has been implemented and successfully applied to small sets of protocols. In particular, we discovered an undocumented family of attacks, that may arise when Bauer-Berson-Feiertag and the Woo-Lam authentication protocols are running in parallel. The implementation complexity of the analysis is low polynomial

On Efficient Key Agreement Protocols

A class of efficient key agreement protocols proposed by Boyd is examined. An attack is demonstrated on a round-optimal example protocol of this class, and a simple countermeasure is suggested. The whole class is known to be vulnerable to an attack proposed by Bauer, Berson and Feiertag. A new class of key agreement protocols without this vulnerability but having the same advantages in efficiency is identified, and a number of concrete protocols are suggested

The Interpolating Random Spline Cryptosystem and the Chaotic-Map Public-Key Cryptosystem

The feasibility of implementing the interpolating cubic spline function as encryption and decryption transformations is presented. The encryption method can be viewed as computing a transposed polynomial. The main characteristic of the spline cryptosystem is that the domain and range of encryption are defined over real numbers, instead of the traditional integer numbers. Moreover, the spline cryptosystem can be implemented in terms of inexpensive multiplications and additions. Using spline functions, a series of discontiguous spline segments can execute the modular arithmetic of the RSA system. The similarity of the RSA and spline functions within the integer domain is demonstrated. Furthermore, we observe that such a reformulation of RSA cryptosystem can be characterized as polynomials with random offsets between ciphertext values and plaintext values. This contrasts with the spline cryptosystems, so that a random spline system has been developed. The random spline cryptosystem is an advanced structure of spline cryptosystem. Its mathematical indeterminacy on computing keys with interpolants no more than 4 and numerical sensitivity to the random offset t( increases its utility. This article also presents a chaotic public-key cryptosystem employing a one-dimensional difference equation as well as a quadratic difference equation. This system makes use of the El Gamal’s scheme to accomplish the encryption process. We note that breaking this system requires the identical work factor that is needed in solving discrete logarithm with the same size of moduli

Specifications Database of Security Protocols

Původní protokoly, které vznikaly v počátcích vývoje počítačových sítí, již nejsou pro zajištění potřebné bezpečnosti dostačující. Proto se stále vyvíjejí a implementují protokoly nové. Důležitou součástí tohoto procesu je formální verifikace. Jde o analýzu protokolu po formální stránce, kdy se zjišťuje, zda lze protokol úspěšně napadnout. Diplomová práce se zabývá analýzou vybraných bezpečnostních protokolů a nástrojů pro jejich formální verifikaci. Výstupem praktické části je databáze specifikací protokolů v LySa kalkulu a výsledky jejich verifikace nástrojem LySatool.Original protocols, which were created during early development of computer networks, no longer provide sufficient security. This is the reason why new protocols are developed and implemented. The important component of this process is formal verification, which is used to analyze the developed protocols and check whether a successful attack is possible or not. This thesis presents selected security protocols and tools for their formal verification. Further, the selected protocols are specified in LySa calculus and results of their analysis using LySatool are presented and discussed.