Introduction of Cryptography

History & asymmetric

, What is Cryptography:
- Crypto: hidden secret
- Graphy: writing
- Secret writing
- Secret way of sending out message no body can read instead of receiver
- Lock & keys
- Plain text → Encrypting → symbols/ letters that not the same as the
text (cipher text)
- Sent out ciphertext → Decryption → turn it back to plain text

History of Cryptography:
- Used in: Military, web browsing, email, social media, online transaction, cloud services
- Only I can read it, don’t want others to read it
- Storage & message sending
- Julius Caesar → Caesar cipher
- AI Kindi: how to encrypt & decrypt + breaking the code
- Vigenere: use of encryption key to make ciphertext
- Modern Age
- Public key cryptography:
- RSA:
- Elliptic curves: e.g. BitCoin
- Goals of cryptography:
- Confidentiality (secrecy): No one else can read the data
- Integrity (cannot altered, modified/ damaged accidentally by an
attacker) → hashing function to check
- Authentication: make sure the message come from the correct person
- Non-repudiation: the sender of the message cannot deny a comment/ action

Practice Assignment: Alice & Bob’s conundrum