445-In Class-Assignment 8

445-In Class-Assignment 8   Chapter 6 Task 1 Question 6.1 In triple encryption, a plaintext block is encrypted by passing it through an encryption algorithm first. The resulting ciphertext is passed through the same algorithm again. Ultimately, the ciphertext from the subsequent operation is encrypted through the same algorithm the third time. Question 6.2 These are attacks against double encryption algorithms; it requires known pairs for the attack to be successful, for Example of ciphertext and plaintext. The plain text is encrypted to produce an intermediate quantity is double encryption. The decryption follows the same process. , a table lookup technique is used, which tries all the possible pairs keys to improve the brute-force. Question 6.3 In triple encryption, three distinct keys can be used for each of the three stages; however, a single key can be used for all the three-encryption steps. Question 6.4 Decryption, in the second phase of cryptography, has no major significance. The only benefit of 3DES is that it allows users to decrypt data encrypted using the older single DES by repeating the keys. Question 6.5
  1. A significant period should be used in the encryption sequence.
  2. The stream of the key should have the property of a valid random number as much as possible.
Task 2 Multiple Encryption This is a process of encrypting an encrypted message by either using the same key or different key. It is also referred to as cascade ciphering. Super encryption refers to the over-the-counter encryption of multiple keys. Triple DES In triple-DES (Data Encryption Standard), blocks of cipher algorithms are applied three times to each data block. The size of the key is increased in triple DES to ensure an extra security layer. Every block contains 64 data bits. It has three keys, with 56 bits per key (Rosal & Kumar, 2017). Double DES Advantages
  1. It has a bit of 56-bit key. There are 2^56 probable keys
  2. Encryption and decryption takes the same algorithms
Disadvantages
  1. It has weak keys
  2. Same outputs can be obtained from different S-box
  • For a message encrypted with a specified key which takes the compliments of the encryption, it will have the same encryption of compliment key and complement message
  1. It is possible to brute attack finite times on modern processors.
Triple DES with Two Keys Advantages
  1. Description encryption uses the same structure, and the keys use reverse order.
  2. It easy to avoid weak keys by explicitly testing
  • It is much stronger than double DES
  Disadvantages
  1. It is more susceptible to attacks than triple DES with triple key
  2. It is also vulnerable to known-plaintext attacks.
  Triple DES with Three Keys Advantages 168-bit key length overcomes the vulnerability to brute-force attack of DES Disadvantages
  1. It has a slow processing speed. It runs three times slower than DES
  2. Unsuitable in limited resource platform
  • Only 64-bit block size
  1. For efficiency and security, a larger block is desirable.
    References Rosal, E., & Kumar, S. (2017). A fast FPGA implementation for a triple DES encryption scheme. Circuits and Systems, 8(09), 237.
Date 28 May, 2020