Public‐Key Algorithms

Public-key cryptography algorithms are designed to resist chosen-plaintext attacks,- their security is based both on the difficulty of deducing the secret key from the public key and the difficulty of deducing the plaintext from the ciphertext. In systems where the digital signature operation is the inverse of the encryption operation, this attack is impossible to prevent unless different keys are used for encryption and signatures. Consequently, it is important to look at the whole system and not just at the individual parts. Good public-key protocols are designed so that the various parties can't decrypt arbitrary messages generated by other parties-the proof-of-identity protocols are a good example. This chapter discusses a list of public-key algorithms including knapsack algorithm, RSA, Pohlig-Hellman encryption scheme, Rabin's scheme, ElGamal scheme, McEliece algorithm and elliptic curve cryptosystems. Some cryptographers have developed generalizations of RSA that use various permutation polynomials instead of exponentiation.