Cryptography Concepts and Security Analysis

Posted by on Jan 22, 2025 in Information Consulting and Management | 0 comments

1. Consider the mono-alphabetic substitution cipher (Lecture 1, slide 20). What is the size of its key space? -26!

2. Consider the poly-alphabetic substitution cipher (Lecture 1, slide 22). What is the size of its key space? -26^t (that is, 26 to the power of t)

3. You know that a meaningful plaintext in a language with an x-letter alphabet is encrypted using either the mono-alphabetic substitution cipher or the poly-alphabetic substitution cipher (with a key of t random numbers in [1,x], for a known

Read More

Cryptography: Concepts, Algorithms, and Security

Posted by on Jan 11, 2025 in Information Consulting and Management | 0 comments

Prime Numbers, GCD, and Congruence

Prime Numbers: Numbers > 1 with no divisors other than 1 & itself.

GCD: Largest positive integer dividing 2 numbers without a remainder.

Congruence: 2 numbers are congruent modulo N if they have the same remainder when divided by N (A ≡ B mod N).

Classical vs. Modern Cryptography

Classical Cryptography:

  1. Based on secrecy of the encryption algorithm.
  2. Key distribution was physical & therefore not as secure.
  3. Encryptions like the Caesar cipher were susceptible
Read More