RSA algorithms is a milestone in the development of cryptography, Comment and Write its step?

Diffie and Hellman introduced a new approach to cryptography, and challenged cryptologist to design a general-purpose encryption algorithm that satisfies the public-key encryption requirements. One of the first responses to the challenge was developed in 1977 by Ron Rivest, Adi Shamir, Len Adleman at MIT. Since then, the Rivest-Shamir-Adleman (RSA) scheme has become the most widely accepted and implemented general-purpose approach to public-key encryption.
The RSA scheme is a block cipher. Each plaintext block is an integer between 0 and n − 1 for some n, which leads to a block size ≤ log2(n). The typical size for n is 1024 bits. The details of the RSA
algorithm are described as follows.

Key generation:

  1. Pick two large prime numbers p and q, p /= q;
  2. Calculate n = p × q;
  3. Calculate _(n) = (p − 1)(q − 1);
  4. Pick e, so that gcd(e, _(n)) = 1, 1 < e < _(n);
  5. Calculate d, so that d ・ e mod _(n) = 1, i.e., d is the multiplicative inverse of e in mod _(n);
  6. Get public key as KU = {e, n};
  7. Get private key as KR = {d, n}.

Encryption:
For plaintext block P < n, its ciphertext C = Pe mod n.

Decryption:
For ciphertext block C, its plaintext is P = Cd mod n.

RSA is secure:
The premise behind RSA’s security is the assumption that factoring a big number (n into p, and q) is hard. And thus it is difficult to determine _(n). Without the knowledge of _(n), it would be hard to
derive d based on the knowledge of e. However factoring n is not the only way to break RSA.

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