WebFund 2016W Lecture 18
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Video
The video for the lecture given on March 17, 2016 is now available.
Notes
In Class
(This is lecture 18, not 17!)
Lecture 18 ---------- Symmetric cryptography - everyone uses the same key - think secret decoder rings - or, file encrypted with AES - secret has to be shared between sender and receiver Public-key cryptography - but what if we don't have a shared secret? - your password isn't good enough, and - websites don't remember your password - and how would you send them your password in the first place - instead, we split the key into two parts - a public key - a private key - whatever one does, the other can undo - if you encrypt with a public key and decrypt with a private key - private one-way communication - e.g., you download Anil's public key and send Anil a secret message - if you encrypt with a private key and decrypt with the public key - that's a digital signature First rule of cryptography - friends don't let friends implement their own crypto - algorithms OR code! Why? You'll miss protections against attacks. Example: timing attacks - can extract secrets by watching execution time - exploits the fact that some numbers take longer to multiply & other operations Everyone else messes up too - so be prepared to update/replace all crypto-related code