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| title | aliases | tags | |
|---|---|---|---|
| cryptography |
|
Crytography arises from the need for confidentiality. Some people say
"if you have nothing to fear you have nothing to hide".
Edward snowden said
"arguing that you don't care about privacy because you have nothing to hide is no different than saying you dont care about free speech because you have nothing to say."
History
One of the earliest known ciphers was the simple subsitution cipher used by julius caesar named the caesar cipher.
Although it a very bad cipher, it still uses the same general process of encryption and decryption.
General Process
- encrypt
- plaintext + key => ciphertext
- key is a secret
- decrypt
- ciphertext + key => plaintext
mathmatically
- c = e(p, k)
- p = d(c, k)
Randomness
randomness is the basis for the theory of cryptography. The aim of encryption is to alter a message (or binary sequence) so that it is maximally random i.e., has the highest entropy, and to remove any sort of pattern.
Terminology/Conventions
- alice, bob, charlie, etc
- mallory -> malicious
- etc
- public vs private domains
- assume communication is public
- assume information is prepared and consumed in private domain
- copy from lecture 5 slides