note05-Computer Network

5. Network security

Passive attacks (UDP packets are intercepted for traffic analysis)

Active attack

1. Tampering (change message stream pseudo-message)

2. Malicious programs (viruses, trojans, worms, bombs)

3. Denial of service Dos

Password system

1. Symmetric key cryptosystem (DES idea)

That is, encryption and decryption of the key k the same

2. Public Key Cryptography (RSA)

A encryption uses PKB public key B to decrypt the corresponding private key SKB

Digital signatures

A-ska Signature Operation-PKB Encryption-transmission-SKB decryption-pka verifying signature

note05-Computer Network