We provide an analysis of the widely deployed SSH protocol’s key exchange mechanism. We exploit the design of the SSH key exchange to perform our analysis in a modular manner. First, a shared secret key is obtained via a Diffie-Hellman key exchange. Next, a transform is applied to obtain the application keys used by later stages of SSH. We define models, following well-established paradigms, th...

The purpose of the paper is to give new key agreement protocols (a multi-party extension of the protocol due to Anshel-Anshel-Goldfeld and a generalization of the Diffie-Hellman protocol from abelian to solvable groups) and a new homomorphic public-key cryptosystem. They rely on difficulty of the conjugacy and membership problems for subgroups of a given group. To support these and other known ...

authenticated Diffie-Hellman key exchange allows two principals communicating over a public network, and each holding public/private keys, to agree on a shared secret value. In this paper we study the natural extension of this cryptographic problem to a group of principals. We begin from existing formal security models and refine them to incorporate major missing details (e.g., strong-corruptio...

Modern cryptography has virtually no provably secure constructions. Starting from the first Diffie–Hellman key agreement protocol (Diffie & Hellman, 1976) and the first public key cryptosystemRSA (Rivest et al., 1978), not a single public key cryptographic protocol has been proven secure. Note, however, that there exist secure secret key protocols, e.g., the one-time pad scheme (Shannon, 1949; ...

ZRTP is a protocol designed to set up a shared secret between two communication parties which is subsequently used to secure the media stream (i.e. the audio data) of a VoIP connection. It uses Diffie-Hellman (DH) key exchange to agree upon a session key, which is inherently vulnerable to active Man-in-the-Middle (MitM) attacks. Therefore ZRTP introduces some proven methods to detect such attac...

The Diie-Hellman key-exchange protocol may naturally be extended to k > 2 parties. This gives rise to the generalized Diie-Hellman assumption (GDH-Assumption). Naor and Reingold have recently shown an eecient construction of pseudo-random functions and reduced the security of their construction to the GDH-Assumption. In this note, we prove that breaking this assumption modulo a composite would ...

Abstract All instances of the semidirect key exchange protocol, a generalisation famous Diffie-Hellman satisfy so-called telescoping equality; in some cases, this equality has been used to construct an attack. In report, we present computational evidence suggesting that instance scheme called “MOBS (matrices over bitstrings)” is example where too many solutions be practically viable means conduct

Authenticated Diffie-Hellman key exchange allows two principals communicating over a public network, and each holding public/private keys, to agree on a shared secret value. In this paper we study the natural extension of this cryptographic problem to a group of principals. We begin from existing formal security models and refine them to incorporate major missing details (e.g., strong-corruptio...

In this paper we identify the (P, Q)-DDH assumption, as an extreme, powerful generalization of the Decisional Diffie-Hellman (DDH) assumption: virtually all previously proposed generalizations of DDH are instances of the (P, Q)-DDH problem. We prove that our generalization is no harder than DDH through a concrete reduction that we show to be rather tight in most practical cases. One important c...

One-pass authenticated key establishment (AKE) protocols are arguably better suited to the ID-based environment than their two-pass counterparts. However, there is no ID-based one-pass AKE protocol proposed in the literature with a proof of security in an appropriate model. This paper addresses the current gap by proposing a new ID-based one-pass AKE protocol and proving it secure in a formal m...