This artifact demonstrates my understanding of fundamental cryptographic concepts used to protect digital information. In this assignment, I applied mathematical and analytical techniques to study symmetric encryption, pseudorandom generators, and pseudorandom functions. The work required careful reasoning and step-by-step calculations to understand how cryptographic algorithms generate secure outputs and protect communication systems. 

One part of the assignment involved analyzing a linear congruential generator (LCG) and calculating the sequence of values produced by the generator using modular arithmetic. This exercise demonstrated how pseudorandom number generators operate and how predictable patterns can appear when generators rely on simple linear functions. Understanding these patterns is important because weak randomness can create vulnerabilities in cryptographic systems. 

Another section required analyzing a 5-bit Linear Feedback Shift Register (LFSR) and determining the first 30 output bits as well as the period of the generator. This task showed how LFSRs produce pseudorandom sequences and how their internal structure affects the length of the generated sequence. The assignment also explored the weaknesses of linear generators and how attackers may predict outputs if the internal state is recovered. 

The assignment also included a detailed analysis of the DES f-function, where I expanded a 32-bit input to 48 bits, performed XOR operations with a subkey, applied S-box substitutions, and computed the final permutation output. This process illustrates the complexity of block cipher operations and how multiple transformations work together to secure encrypted data. 

Overall, this artifact demonstrates my ability to apply cryptographic theory, mathematical reasoning, and algorithmic analysis, which are essential skills for understanding how modern encryption systems protect sensitive information.

Skill: Cryptography and Secure Communication

because it demonstrates:

• modular arithmetic and cryptographic calculations
• pseudorandom generator analysis
• LFSR keystream generation
• DES block cipher operations
• Understanding cryptographic weaknesses