# The Six Principle Elements of a Public-Key Cryptosystem

1)What are the six principle elements of a public-key cryptosystem?

2)What are three broad categories of applications of public-key cryptosystems?

3)What is a function that maps a domain into a range such that every function value has a unique inverse, with the condition that the calculation of the function is easy whereas the calculation of the inverse is infeasible?

4)What is a function that is easy to calculate in one direction and infeasible to calculate in the other direction unless certain additional information is known?

5)In a public-key system using RSA, you intercept the ciphertext C = 10 sent to a user whose public key is e = 5, n = 35. What is the plaintext M?

6)In an RSA system, the public key of a given user is e = 31, n = 3599. What is the private key of this user?

Hing: First us trial and error to determine p and q; then use the extended Euclidean algorithm to find the multiplicative inverse of 31 modulo φ(n).