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Publication# When Stream Cipher Analysis Meets Public-Key Cryptography

Abstract

Inspired by fast correlation attacks on stream ciphers, we present a stream cipher-like construction for a public-key cryptosystem whose security relies on two problems: finding a low-weight multiple of a given polynomial and a Hidden Correlation problem. We obtain a weakly secure public-key cryptosystem we call TCHo (as for Trapdoor Cipher, Hardware Oriented). Using the Fujisaki-Okamoto construction, we can build an hybrid cryptosystem, TCHon-FO, resistant against adaptive chosen ciphertext attacks.

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Related concepts (4)

Caesar cipher

In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, would be replaced by , would become , and so on. The method is named after Julius Caesar, who used it in his private correspondence.

Public-key cryptography

Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key. Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions. Security of public-key cryptography depends on keeping the private key secret; the public key can be openly distributed without compromising security.

Stream cipher

A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. Since encryption of each digit is dependent on the current state of the cipher, it is also known as state cipher. In practice, a digit is typically a bit and the combining operation is an exclusive-or (XOR).