Session-state Reveal is stronger than Ephemeral Key Reveal: Attacking the NAXOS Authenticated Key Exchange protocol

In the papers Stronger Security of Authenticated Key Exchange [LLM07, LLM06], a new security model for key exchange protocols is proposed. The new model is suggested to be at least as strong as previous models for key exchange protocols. In particular, the model includes a new notion of an Ephemeral Key Reveal adversary query, which is claimed in [LLM06, Oka07, Ust08] to be at least as strong as existing definitions of the Session-state Reveal query. We show that for some protocols, Session-state Reveal is strictly stronger than Ephemeral Key Reveal. In particular, we show that the NAXOS protocol from [LLM07, LLM06] does not meet its security requirements if the Session-state Reveal query is allowed in the security model

Human Computing for Handling Strong Corruptions in Authenticated Key Exchange

International audienceWe propose the first user authentication and key exchange protocols that can tolerate strong corruptions on the client-side. If a user happens to log in to a server from a terminal that has been fully compromised, then the other past and future user's sessions initiated from honest terminals stay secure. We define the security model for Human Authenticated Key Exchange (HAKE) protocols and first propose two generic protocols based on human-compatible (HC) function family, password-authenticated key exchange (PAKE), commitment, and authenticated encryption. We prove our HAKE protocols secure under reasonable assumptions and discuss efficient instantiations. We thereafter propose a variant where the human gets help from a small device such as RSA SecurID. This permits to implement an HC function family with stronger security and thus allows to weaken required assumptions on the PAKE. This leads to the very efficient HAKE which is still secure in case of strong corruptions. We believe that our work will promote further developments in the area of human-oriented cryptography

Password-Authenticated Public-Key Encryption

We introduce password-authenticated public-key encryption (PAPKE), a new cryptographic primitive. PAPKE enables secure end-to-end encryption between two entities without relying on a trusted third party or other out-of-band mechanisms for authentication. Instead, resistance to man-in-the-middle attacks is ensured in a human-friendly way by authenticating the public key with a shared password, while preventing offline dictionary attacks given the authenticated public key and/or the ciphertexts produced using this key. Our contributions are three-fold. First, we provide property-based and universally composable (UC) definitions for PAPKE, with the resulting primitive combining CCA security of public-key encryption (PKE) with password authentication. Second, we show that PAPKE implies Password-Authenticated Key Exchange (PAKE), but the reverse implication does not hold, indicating that PAPKE is a strictly stronger primitive than PAKE. Indeed, PAPKE implies a two-flow PAKE which remains secure if either party re-uses its state in multiple sessions, e.g. due to communication errors, thus strengthening existing notions of PAKE security. Third, we show two highly practical UC PAPKE schemes: a generic construction built from CCA-secure and anonymous PKE and an ideal cipher, and a direct construction based on the Decisional Diffie-Hellman assumption in the random oracle model. Finally, applying our PAPKE-to-PAKE compiler to the above PAPKE schemes we exhibit the first 2-round UC PAKE\u27s with efficiency comparable to (unauthenticated) Diffie-Hellman Key Exchange

Lattice-based Authenticated Key Exchange with Tight Security

We construct the first tightly secure authenticated key exchange (AKE) protocol from lattices. Known tight constructions are all based on Diffie-Hellman-like assumptions. Thus, our protocol is the first construction with tight security from a post-quantum assumption. Our AKE protocol is constructed tightly from a new security notion for key encapsulation mechanisms (KEMs), called one-way security against checkable chosen-ciphertext attacks (OW- ChCCA). We show how an OW-ChCCA secure KEM can be tightly constructed based on the Learning With Errors assumption, leading to the desired AKE protocol. To show the usefulness of OW-ChCCA security beyond AKE, we use it to construct the first tightly bilateral selective-opening (BiSO) secure PKE. BiSO security is a stronger selective-opening notion proposed by Lai et al. (ASIACRYPT 2021)

On the Relations Between Diffie-Hellman and ID-Based Key Agreement from Pairings

This paper studies the relationships between the traditional Diffie-Hellman key agreement protocol and the identity-based (ID-based) key agreement protocol from pairings. For the Sakai-Ohgishi-Kasahara (SOK) ID-based key construction, we show that identical to the Diffie-Hellman protocol, the SOK key agreement protocol also has three variants, namely \emph{ephemeral}, \emph{semi-static} and \emph{static} versions. Upon this, we build solid relations between authenticated Diffie-Hellman (Auth-DH) protocols and ID-based authenticated key agreement (IB-AK) protocols, whereby we present two \emph{substitution rules} for this two types of protocols. The rules enable a conversion between the two types of protocols. In particular, we obtain the \emph{real} ID-based version of the well-known MQV (and HMQV) protocol. Similarly, for the Sakai-Kasahara (SK) key construction, we show that the key transport protocol underlining the SK ID-based encryption scheme (which we call the "SK protocol") has its non-ID counterpart, namely the Hughes protocol. Based on this observation, we establish relations between corresponding ID-based and non-ID-based protocols. In particular, we propose a highly enhanced version of the McCullagh-Barreto protocol

On Vulnerabilities of the Security Association in the IEEE 802.15.6 Standard

Wireless Body Area Networks (WBAN) support a variety of real-time health monitoring and consumer electronics applications. The latest international standard for WBAN is the IEEE 802.15.6. The security association in this standard includes four elliptic curve-based key agreement protocols that are used for generating a master key. In this paper, we challenge the security of the IEEE 802.15.6 standard by showing vulnerabilities of those four protocols to several attacks. We perform a security analysis on the protocols, and show that they all have security problems, and are vulnerable to different attacks

A modified eCK model with stronger security for tripartite authenticated key exchange

Since Bellare and Rogaway presented the first formal security model for authenticated key exchange (AKE) protocols in 1993, many formal security models have been proposed. The extended Canetti-Krawczyk (eCK) model proposed by LaMacchia et al. is currently regarded as the strongest security model for two-party AKE protocols. In this paper, we first generalize the eCK model for tripartite AKE protocols, called teCK model, and enhance the security of the new model by adding a new reveal query. In the teCK model, the adversary has stronger powers, and can learn more secret information. Then we present a new tripartite AKE protocol based on the NAXOS protocol, called T-NAXOS protocol, and analyze its security in the teCK model under the random oracle assumption