This lecture explains why randomness is so important to security, using examples such as TLS session keys and TCP initial sequence numbers. It reviews the inadequacies of conventional pseudo-random number generators (PRNGs) for security purposes and explores more secure alternatives. It highlights the importance of initializing cryptographically secure pseudo-random number generators (CSPRNGs) with a good source of entropy, and discusses some of the entropy sources that can be used to seed CSPRNGs.

• Lecture video
• Slides (PDF)
• Code examples
• Exercises:
  • Secure Randomness in Python & Java
• Other resources:
  • Untwister - seed recovery tool for PRNGs
  • Strange attractors & TCP sequence number analysis
  • RFC 6528: Defending Against Sequence Number Attacks
  • HotBits: random numbers via radioactive decay
  • Entropy from silkworms (yes, really!)
  • Cloudflare blog post on LavaRand
  • CrossTalk attack - CVE-2020-0543 (PDF)
  • Myths about /dev/urandom