Explain the principles and applications of public-key cryptography in secure communication systems.

Public-key cryptography, also known as asymmetric cryptography, is a cryptographic system that uses two mathematically related keys: a public key and a private key. This type of cryptography was a significant advancement in the field of secure communication systems as it addressed key distribution challenges present in symmetric key cryptography. 1. Principles of Public-Key Cryptography: a. Key Pair Generation: In public-key cryptography, each user generates a unique key pair consisting of a public key and a corresponding private key. The keys are mathematically related, but it is computationally infeasible to derive the private key from the public key. b. Encryption: The public key is widely distributed and can be freely shared with others. When a user wants to send an encrypted message to another user, they use the recipient's public key to encrypt the message. The encryption process transforms the plaintext into ciphertext, which can only be decrypted using the corresponding private key. c. Decryption: The recipient, who possesses the private key, c....