This document presents a comprehensive solution to a security in computing and information technology assignment, covering various cryptographic techniques. The assignment includes cryptanalysis of simple substitution ciphers, double transposition ciphers, and complex substitution ciphers. It also addresses the application of hash algorithms, specifically SHA-256, in a sealed bid auction scenario. Furthermore, the solution demonstrates the encryption and decryption steps using the Paillier encryption algorithm. The solution provides step-by-step explanations and calculations for each problem, offering a detailed understanding of the concepts and practical applications of these security measures. The assignment covers topics from lectures 1-4 on security in computing and information technology, including symmetric and asymmetric key cryptography.