Cryptography

Introduction

EncryptionThe art (or science) of putting messages into

a code, and the study of those coding techniques.

DecryptionThe means by which to bring out the meaning

from a coded message.

Simple Techniques

Original text “testing” Reversing text

“gnitset” Shifting text

“uftujoh” Flipping text

“ettsnig” Caeser cipher

Multi-shift (this one is by 2) “vguvkpi”

Examples

Cryptography Public Key Encryption

You create a private key/public key pair If a message is encrypted with your private key, only your public

key will decrypt it Publish your public key on web sites or send it to people via e-mail

Uses If you want to send a private message to another person, encrypt it

with their public key (only they can decrypt it with their private key) Digital Signatures

Encrypt with your private key first and then their public key

PGP (Pretty Good Privacy) One version of this technology

Example