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Journals and Conferences
An important property of a hash function is the performance. We study fast iterated hash functions based on block ciphers. These hash functions and their compression functions are analyzed in the standard black-box model. We show an upper bound on rate of any collision resistant hash function. In addition, we improve known bound on the rate of collision… (More)
Designated verifier signature schemes allow a signer to convince only the designated verifier that a signed message is authentic. We define attack models on the unforgeability property of such schemes and analyze relationships among the models. We show that the no-message model, where an adversary is given only public keys, is equivalent to the model, where… (More)
Boolean functions used in cryptographic applications have to satisfy various cryptographic criteria. Although the choice of the criteria depends on the cryptosystem in which they are used, there are some properties (balancedness, nonlinearity, high algebraic degree, correlation immunity, propagation criteria) which a cryptographically strong Boolean… (More)
Batch verification of digital signatures is used to improve the computational complexity when large number of digital signatures must be verified. Lee at al.  proposed a new method to identify bad signatures in batches efficiently. We show that the method is flawed.
The security of iterated hash functions relies on the properties of underlying compression functions. We study highly efficient compression functions based on block ciphers. We propose a model for highrate compression functions, and give an upper bound for the rate of any collision resistant compression function in our model. In addition, we show that… (More)
Simultaneous contract signing is a two-party cryptographic protocol: two mutually suspicious parties wish to exchange signatures on a contract. We propose novel and efficient protocol for contract signing based on a construction by Even, Goldreich, and Lempel. We focus on the reduction of on-line computational complexity of the protocol. A significant part… (More)
We show that the protocol recently proposed in  for securing multicast communication is completely insecure.
We show that a recently proposed password authentication scheme based on geometric hashing has several security weaknesses, and that the use of this scheme should be avoided in practice.
Scrambled Burrows-Wheeler transform  is an attempt to combine privacy (encryption) and data compression. We show that the proposed approach is insecure. We present chosen plaintext and known plaintext attacks and estimate their complexity in various scenarios.