Uploaded December 2018 | Updated September 2026, 2 weeks ago

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How many people need to be in a room before there’s a 50% chance that two of them share the same birthday? Is it about 180, since that’s around half of 365? Is it only 100? The real answer is surprisingly much, much smaller.

If you have just 23 people in a room, the odds of whether two get presents on the same day is a coin flip. Get 50 people together and that shared-birthday probability skyrockets to 97%. A handful more and it’s a virtual statistical certainty.

Really? Yes, really! With the aid of tiny plastic babies and some mathematics, Kevin proves and visualizes this surprising veridical paradox.

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Birthday Attack Example In Hacking
youtube.com/watch?v=4shxYyV4O_k

Birthday Attack Hash Collision
youtube.com/watch?v=18ihbf1EqRw

Hashing Algorithms And Security - Computerphile
youtube.com/watch?v=b4b8ktEV4Bg

Discussion On The Birthday Attack
youtube.com/watch?v=2bEL3ok8D70

The Birthday Attack
danielmiessler.com/study/birthday_attack

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Hosted, Produced, And Edited by Kevin Lieber
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