[Network] Network Security

1 What's network securityaccess && understand && modification

2 Principles of Cryptographysymmetric key
Encryption key public decryption key secret

2.1 symmetric Key

Substitution cipher:encryption on a side, decryption on another side.

Des:data Encryption Standard

56-bit symmetric key 64-bit plaintext input

aes:advanced Encryption Standard

3 Message Integrity

3.1 Message authentication Codehash code used Belowmake secret encrypted
3.2 Digital Signatures

-From Wiki

Hash h (m) first, then sign it Ks (H (m))

Send both clear message m and Ks (H (m)) to receiver. Receiver Hash m and decrypt H (m), to compare them whether they is same.

Certification authorities

The third company to verify the public key of Bob ' s.

4 End Point Authentication

4.1 Authentication

Other method can is attacked by other host playback process.

5 Securing e-mail

5.1 Secrecy
Sender: 1. Random symmetric private key, Ksy 2. Message m, Ks (m) 3. Use receiver's public key to encrypt the Ks, Kry (Ks) 4. Send both Ksy (m) and Kr (Ks) to receiver
Receiver: 1. Use own public key to decrypt the Ksy 2. Use Ksy to decrypt message m

5.2 Sender Authentication
Sender: 1. Sign the message m 2. Send both clear message m and signed message Ksen (H (m)) Receiver: decrypt the signed message.
5.3 Combinationthree Keys:sender sign key, receiver public key, symmetric key

6 Securing Tcp:ssl

6.1 Service

parts:client/server authentication, data encryption

6.2 Process

1. Handshake Establish TCP connection Authentication2. Key derivation 4 keys MAC key and Encrption Key3. Data Transfer compute mac encrypt data and Mac form SSL format record

6.3 mechanism

Apply for key for encryption and keep secret between server and client.

7 Network Layer:ipsecah or ESP

8 Wireless LANs

Wep

9 Firewall and Idsids:inspection and Correclation