Key Exchange

This clip from the 2008 Royal Institution Christmas Lectures shows a simple demonstration of how two people can agree on a secret key, even though all of their communications are carried out in public. In the electronic world, secret key exchange allows computers to communicate securely, and is used, for example, when you give your credit card information to an on-line shop.
You can watch the 2008 Royal Institution Christmas Lectures in full at: research.microsoft.com/~cmbishop or by visiting the Royal Institution web site.
There is a dedicated web site to accompany the 2008 Christmas Lectures, with ten interactive games as well as downloadable PDF instructions for experiments which can be conducted at home or at school: www.rigb.org/christmaslectures08

[@ron_con]

That's the best explanation of key exchange that I've ever seen. Kudos!

[@ajnbin]

A perfect example of ingenuous and simple explanation

[@CarrollCanada]

Wow thank you so much! This clears all confusion i've had with Diffie Hellman. Greatest video ever.

[@thafrostable]

Wow thanks, ive been studying the theory of key exchange for a while but didnt quite get it there was a missing piece but this video makes it so simple and now its click to how it actually works congrats... u guys should do more videos lol

[@mentin]

Nice, although I think it hides real complexity from kids - finding "locks" that are both associative (most are not) and do not leak information (say simple XOR with private key - associative, but trivial to break when used in this scheme).

[@ChosenV]

I love these padlocks and keys where i can find it to buy???

[@chintandd]

Excellent video - but if this could be explain with private key and public key combination (things we read in books)....then it could be awesome

[@joe501ut]

amazing,the first time i heard about diffie hellman was after graduation from engineering school

[@whitetiger78]

Great Video really made PKI clear. Thanks for Posting this!

[@colinmaharaj]

I still thing they shoud be teaching modular exponent arithmetic to make things even more clearer. But the demo was excellent!!!

[@ChosenV]

@southwoodside Red and Green Key is the private key...nobody can see this...Red and Green Padlock is the Encryption (ex. RSA)....once both know they are secure (Certifcate both have the correct key to decrypt) then the blue key both use it to send msgs encrypted.!

[@southwoodside]

I don't see the need for the red lock. Could he not just use the blue lock ? Also as O2Matthewj below comments, couldn't be intercepted and returned deceptively ?

[@vvurx]

great video

[@GeorgeHafiz]

PIN DROP MOMENT! Finally I understand how public key exchanges work! Cheers guys. Also, Britain FTW.