Answer to Question #318809 in Computer Networks for Nickname

Question

Discussion Topic: Cryptography

Give a brief overview of this area. Describe and list several Cipher methods. Explain Cryptographic algorithms and give several examples.

Answer 1

Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it.

Different types of ciphers

Substitution Cipher: This offers an alternative to the plaintext. It is also known as Caesar cipher.

Polyalphabetic Substitution Cipher: In this cipher, a mixed alphabet is used to encrypt the plaintext, but at random points it would change to a different mixed alphabet which indicates the change with an uppercase letter in the Ciphertext.

Transposition Cipher: This cipher is also known as Rail Fence Cipher and is a permutation of the plaintext.

Permutation Cipher: The positions held by plaintext are shifted to a regular system in this cipher so that the ciphertext constitutes a permutation of the plaintext.

Private-key Cryptography: In this cipher, even the attacker is aware of the plaintext and corresponding ciphertext. The sender and receiver must have a pre-shared key. The shared key is kept secret from all other parties and is used for encryption as well as decryption.

Public-key Cryptography: In this cipher, two different keys - public key and private key - are used for encryption and decryption. The sender uses the public key to perform encryption, whereas the receiver is kept in the dark about the private key. This is also known as asymmetric key algorithm.

There are three general classes of NIST-approved cryptographic algorithms.

Hash functions

A cryptographic hash function does not use keys for its basic operation. This function creates a small digest or “hash value” from often large amounts of data through a one-way process such as:

• Providing source and integrity authentication services by generating message authentication codes (MACs)
• Compressing messages for generating and verifying digital signatures.

Symmetric-key algorithms

a symmetric-key algorithm transforms data to make it extremely difficult to view without possessing a secret key.

The key is considered symmetric because it is used for both encrypting and decrypting.

Asymmetric-key algorithms

asymmetric-key algorithms use paired keys (a public and a private key) in performing their function. The public key is known to all, but the private key is controlled solely by the owner of that key pair. The private key cannot be mathematically calculated through the use of the public key even though they are cryptographically related.