1) ASSIGNMENT 1 FOR DISCUSSION BOARD OF APPLIED CRYPTOGRAPHY AND NETWORK SECURITY (200 words) Explain the following concepts: What is your understanding of the difference between a stream cipher and a...

1.
a)
Block cipher
· The Block Cipher technique encrypts plaintext one block at a time.
· Block Cipher can convert more bits than Stream Cipher, which can only convert bits greater than 64, because it transforms blocks at once.
        Stream cipher
· Stream Cipher encryption converts one byte of plaintext at a time.
· The Stream Cipher, on the other hand, can only change eight bits at a time.

b)
    
· Ciphetext only: The brute-force approach, which involves trying each key, is one potential assault in these conditions. If the key space is especially big, this gets challenging. As a result, the attacker must rely on the ciphertext's statistical test assessment.
· Known plaintext: The analyzer may have access to one or more plaintext communications and their encryptions. The analyst may be able to determine the key by modifying the known plaintext with this data.
c)
· Unconditionally secure cipher: If the cypher text is encrypted, the approach is guaranteed to be secure. Regardless matter how much ciphertext is supplied, it creates insufficient information to discover the linked plaintext.
· Computationally secure cipher: No matter how much ciphertext is available, an encryption technique is guaranteed to be secure if the ciphertext it generates does not include enough information to locate the related plaintext.
d)
Because the Data Encryption Standard (DES) algorithm was shown to be readily hacked by hackers, it was superseded with Triple DES. Triple DES was formerly the most prevalent and best practise in the industry.
Triple DES employs three distinct 56-bit keys. Experts claim that a key strength of 112 bits is more accurate, even if the key is 168 bits long overall. Despite being phased out gradually, the Advanced Encryption Standard (AES) has effectively replaced Triple DES.
2.

    Monoalphabetic Cipher:
A mono-alphabetic substitution cypher is one type of replacement cypher that operates by substituting identical letters in the ciphertext with related letters in the plaintext. The term "mono," which meaning "one," refers to the fact that each letter in the plaintext has just one ciphertext.
Throughout the encryption process, In a mono-alphabetic cypher, the connection between a symbol in the plaintext and a symbol in the cypher text is always one-to-one, a kind of substitution. . It is thought that cryptography can easily break these...