Pigeonhole principle and collision inevitability

Big thank you to DeleteMe for sponsoring this video. Use my link http://joindeleteme.com/Bombal to receive a 20% discount or use the QR Code in the video. In this interview, David Bombal sits down with Dr. Mike Pound (Computerphile) to clear up one of the biggest crypto misconceptions on the Internet: hashing is not encryption, and hash functions are not reversible. In this video you’ll learn what a hash function actually does (a deterministic, fixed-length, “random-looking” summary of data) and why the whole point is that you cannot take a hash and reconstruct the original file. Dr Mike explains the key properties of secure hashing, including the avalanche effect (tiny input change, massive output change), and why older algorithms like MD5 and SHA-1 became unsafe due to collisions. We also cover what “collisions” really mean, why they must exist in theory (the pigeonhole principle) and why they can appear sooner than expected (the birthday paradox). Then we tackle the YouTube-comments classic: rainbow tables. If hashes are one-way, how do attackers “crack” passwords? The answer: they don’t reverse hashes. They guess passwords, hash them forward, and match the results. Mike breaks down how rainbow tables speed this up with precomputed hashes, and why salting makes those precomputations far less effective by forcing attackers to redo work per user. Finally, we zoom out into modern cryptography: why SHA-2 is widely used today, why SHA-3 exists as a structurally different backup option, what length extension attacks are, and what quantum computing changes (and doesn’t change) for hashing and encryption. We also touch on how hashes power digital signatures, file integrity checks (like verifying an ISO download), and why AES dominates symmetric encryption. // Mike's SOCIAL // X: / _mikepound // YouTube Video REFERENCE // SHA: Secure Hashing Algorithm: • SHA: Secure Hashing Algorithm - Computerphile Birthday Paradox: • Hash Collisions & The Birthday Paradox - C... The Next Big SHA? SHA3 Sponge Function Explained: • The Next Big SHA? SHA3 Sponge Function Exp... // David's SOCIAL // Discord: discord.com/invite/usKSyzb Twitter: www.twitter.com/davidbombal Instagram: www.instagram.com/davidbombal LinkedIn: www.linkedin.com/in/davidbombal Facebook: www.facebook.com/davidbombal.co TikTok: tiktok.com/@davidbombal YouTube: / @davidbombal Spotify: open.spotify.com/show/3f6k6gE... SoundCloud: / davidbombal Apple Podcast: podcasts.apple.com/us/podcast... // MY STUFF // https://www.amazon.com/shop/davidbombal // SPONSORS // Interested in sponsoring my videos? Reach out to my team here: sponsors@davidbombal.com // MENU // 0:00 - Coming up 01:09 - DeleteMe sponsored segment 02:54 - Hashing is not Encryption // Encryption and Hashing explained 09:47 - Hash functions are irreversible 15:22 - How hashing works 17:23 - Why MD5 is bad 20:09 - Recommended hashing function 21:47 - Birthday paradox explained 23:39 - Rainbow table explained 29:44 - Salting explained 33:35 - Pigeon Hole principle explained 36:35 - SHA-2 is the answer 37:17 - SHA-3 vs SHA-2 40:42 - The effect of quantum computing 42:47 - Quick summary 43:52 - Sign-In with private key 45:21 - Avalanche effect explained 49:10 - Where to learn more about hash functions 50:27 - Conclusion Please note that links listed may be affiliate links and provide me with a small percentage/kickback should you use them to purchase any of the items listed or recommended. Thank you for supporting me and this channel! Disclaimer: This video is for educational purposes only. #cryptography #hashing #encryption