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Security and Cryptography

Security and Cryptography

Table of Contents

Entropy

correct horse battery staple

Hash functions

$ printf 'hello' | sha1sum
aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d
$ printf 'hello' | sha1sum
aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d
$ printf 'Hello' | sha1sum 
f7ff9e8b7bb2e09b70935a5d785e0cc5d9d0abf0

Applications

Key derivation functions

Applications

Symmetric Cryptography

Hiding message contents with symmetric cryptography

keygen() -> key  (this function is randomized)

encrypt(plaintext: array<byte>, key) -> array<byte>  (the ciphertext)
decrypt(ciphertext: array<byte>, key) -> array<byte>  (the plaintext)

Applications

Asymmetric cryptography

Public-key cryptography

Two keys with two roles

  1. Private key is kept private
  2. Public key is publicly shared without compromising security

Functionality for encrypt, decrypt, sign, verify:

Lock analogy

Applications

Key distribution

Case Studies

Resources


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