Threshold cryptography increases security and resilience by sharing a private cryptographic key over different devices. Many personal devices, however, are not suited for threshold schemes, because they do not offer secure storage, which is needed to store shares of the private key. We present a solution that allows to include devices without them having to store their share. Shares are stored ...

This report gives a novel technique of image encryption and authentication by combining elements of Visual Cryptography and Public Key Cryptography. A prominent attack involving generation of fake shares to cheat honest users has been described and a demonstration of the proposed system employing a centralised server to generate shares and authenticate them on the basis of requests is made as a...

Kerberos is a protocol for verifying the identity of principals (e.g., a workstation user or a network server) on an open network. The Kerberos protocol provides a facility called pre-authentication. Pre-authentication mechanisms can use this facility to extend the Kerberos protocol and prove the identity of a principal. This document describes a more formal model for this facility. The model d...

We propose a new protocol providing cryptographically secure authentication to unaided humans against passive adversaries. We also propose a new generic passive attack on human identification protocols. The attack is an application of Coppersmith’s baby-step giantstep algorithm on human identification protcols. Under this attack, the achievable security of some of the best candidates for human ...

One of the main applications of Physical Unclonable Functions (PUFs) is unique key generation. While the advantages of PUFbased key extraction and embedding have been shown in several papers, physical attacks on it have gained only little interest until now. In this work, we demonstrate the feasibility of a differential power analysis attack on the error correction module of a secure sketch. Th...

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 ...

We report experiments on the security of the GGH-like cryptosystem proposed by Micciancio. Based on these experiments, we conclude that the system can be securely used only in lattice dimensions ≥ 782. Further experiments on the efficiency of the system show that it requires key sizes of 1MByte and more and that the key generation as well as the decryption take inacceptibly long. Therefore, Mic...

Anti-P2P companies have begun to launch Internet attacks against BitTorrent swarms. In this paper, we analyze how successful these attacks are at impeding the distribution of targeted files. We present the results of both passive and active measurements. For our active measurements, we developed a crawler that contacts all the peers in any given swarm, determines whether the swarm is under atta...

Following the vision of Ambient Intelligence (AmI), this paper introduces and evaluates a novel security scheme that takes the advantage of the unpredictable and erratic behavior of wireless communication to generate secret keys. The main advantage is that the secret key generation is applicable to every wireless device, independently of their hardware characteristics as it only requires a wire...