Lab Notes: 2025-11-17

Overview

A full day focused on hashing algorithms, file integrity checks, and understanding how verification systems work in real environments. Strengthened command-line skills and built deeper intuition around hash properties and checksum validation.

Cybersecurity Topics Covered

  • Identifying hash modes for SHA1, Cisco ASA MD5, and generic hashes.
  • Determining hash length and structure to infer algorithm type.
  • Understanding how file verification works using checksum files.
  • Learning what md5sum -c actually verifies internally.
  • Understanding how attackers and defenders use checksums to confirm integrity.
  • Practiced base64 encoding using CLI.

Key Commands Practiced

# Generate MD5 hash
md5sum passport.jpg

# Verify hash against checksum file
md5sum -c checksum.txt

# Base64 encoding
echo -n "message" | base64

Important Notes

  • Verification (-c) compares computed hash to the stored hash in a checksum file.
  • Learned example checksum filenames: hashes.md5, checksums.txt, files.sha1, verify.md5, integrity.sum.
  • Clear separation between hashing for storage, hashing for verification, and hashing for attack enumeration.