Yasuyuki Murakami

An Implementation of Space-Time Tradeoff Method for Subset Sum Problem

The subset sum problem(SSP) is known to be one of the NP-complete problems. The knapsack public-key cryptosystem is based on SSP. In computer science, a space-time tradeoff method is well-known technique where the computation time can be reduced at the cost of increased memory use. It is known that the space-time tradeoff method can be applied to solve SSP. In this paper, we implement the space-time tradeoff method in order to solve SSP. Moreover, we measure execution time for solving SSP.

A Differential Knapsack Public-Key Cryptosystem

So far the present authors have made an intensive study of using as few trapdoors as possible in the secret sequence based on a probabilistic encryption. In this paper, by following this study, we present a probabilistic differential knapsack PKC with no trapdoor in the secret sequence. We also discuss on the security of the proposed scheme and show that the proposed scheme is secure against the low-density attack and the attack of disclosing secret key.

Knapsack Key-Generation System using JavaScript on Web

Although some studies have been conducted in knapsack cryptosystems, it is not necessarily easy to generate keys in public-key cryptosystem. There are few open, scalability and easy to use systems. For web usage, programs written in JavaScript have high transparency and scalability, and are very suitable for cryptosytems. This paper provides the necessary systems to generate keys, encrypt and decrypt in knapsack cryptosytem, which can be applied to most knapsack PKC by simply defining some functions including generating secret keys, translating into public keys and others. This paper also provides two examples, Merkle-Hellman and shifted odd knapsack PKC.