Hash function is function that accepts input of arbitrary size and produce fixed sized output. Two different inputs is very likely to produce different outputs. Function is irreversible.

Homework: Find document for which CRC32 32 bits signature is 0xbbd1264f.

Symmetric cryptography, AES, one key is used for encryption or decryption. Block algorithims.

Asymmetric cryptography (public and private key). Asymetric signatures.

Master Etherum book

https://github.com/ethereumbook/ethereumbook stop at introduction