W e show how co construct public-key cryptosysterns that are fair, that is, strike a good balance, in a democratic country, between the needs of the Government and those of the Citizens. Fair public-key cryptosystems guarantee that: (1) the systcm cannot be misused by criminal organizations and ( 2 ) the Citizens rnantain exactly the same rights to privacy they currently have under the law. We ...

The public key system proposed by Lin Chang and Lee is insecure even if used as a private key system Index Terms Public key cryptography knapsack cryptosystems This author s research supported by EPSRC Research Grant No GR H This author acknowledges the support of the Nu eld Foundation This author s research supported by a Lloyd s of London Tercentenary Foundation Research Fellowship In the aut...

By introducing extra shields on Shpilrain and Ushakov’s Ko-Lee-like protocol based on the decomposition problem of group elements we propose two new key exchange schemes and then a number of public key cryptographic protocols. We show that these protocols are free of known attacks. Particularly, if the entities taking part in our protocols create their private keys composed by the generators of...

This paper presents and analyzes cryptanalytic attacks on knapsack public key cryptosystems that are based on ideas from Diophantine approximation. Shamir’s attack on the basic Merkle-Hellman knapsack cryptosystem is shown to depend on the existence of ‘‘unusually good’’ simultaneous Diophantine approximations to a vector constructed from the public key. This aspect of Shamir’s attack carries o...

Most of the work in the analysis of cryptographic schemes is concentrated in abstract adversarial models that do not capture sidechannel attacks. Such attacks exploit various forms of unintended information leakage, which is inherent to almost all physical implementations. Inspired by recent side-channel attacks, especially the “cold boot attacks”, Akavia, Goldwasser and Vaikuntanathan (TCC ’09...

Yamamota's notion of partial secrecy is extended to Public Key Cryptosystems: the security of a cryptosystem depends on keeping some function of the original record secret, while sending the relevant message (also a function of the original record). Notions of security and semantic security are introduced and compared for such cryptosystems, and securitypreserving reductions between such system...

Elliptic curve cryptosystems (ECC) are new generations of public key cryptosystems that have a smaller key size for the same level of security. The exponentiation on elliptic curve is the most important operation in ECC, so when the ECC is put into practice, the major problem is how to enhance the speed of the exponentiation. It is thus of great interest to develop algorithms for exponentiation...