Virtual Private Network Chapter 4

Lecturer : Trần Thị Ngọc Hoa2 Objectives  VPN Overview  Tunneling Protocol  Deployment models  Lab Demo

Lecturer : Trần Thị Ngọc Hoa3 Overview of VPN

VPN Concept  Virtual Private Networks are logical network that allows users to securely connect through the internet to a remote private network

VPN Deployment Scenarios  Remote Access VPN

VPN Deployment Scenarios  Extranet VPN ( Site to Site, Router to Router )

VPN Deployment Scenarios  Mixed VPN with Firewall

Lecturer : Trần Thị Ngọc Hoa8 Tunneling  Tunneling is a process of encapsulating a payload protocol into another protocol  Provide a secure path through an untrusted network or an incompatible network.

Lecturer : Trần Thị Ngọc Hoa9 Tunneling Protocol  GRE Generic Routing Encapsulation Cisco Proprietry Tunneling Protocol  PPTP ( with/without MPPE ) Point to Point Tunneling Protocol Microsoft proprietry tunneling protocol  L2TP ( with/without IPSec ) Layer 2 Tunneling Protocol Created by Cisco and Microsoft

IP Security  IP Security Overview  Algorithms  IPSec Protocols Lecturer : Trần Thị Ngọc Hoa10

Lecturer : Trần Thị Ngọc Hoa11 IP Security Overview  Open standard developed by IETF’s IPSec working group.  Security Architecture for the Internet Prototol  Designed to work at Layers 3 and 4 of the OSI model.  IPSec protects data by providing the following services : Data Authentication  Data integrity  Data origin authentication between A pair of gateways A pair of hosts A host and its gateway  Relay protection Encryption  Many different types of algorithm are used in IPSec  2 primary protocols AH – Authentication Header - 51 ESP – Encryption Security Payload - 50

Lecturer : Trần Thị Ngọc Hoa12 Encryption Algorithms  Designed for data confidentiality assurance  2 different methods Symmetrical Asymmetrical

Lecturer : Trần Thị Ngọc Hoa13 Symmetrical Algorithms EncryptDecrypt Data #$ad^&* Data  DES – Data Encryption Standard 56 bit key – 64 data bit block No of Key = 72,000,000,000,000,000  3DES Three phases Encrypt – Decrypt – Encrypt 168 bit key – 64 data bit block  AES – Advanced Encryption Standard bit key Session key

Lecturer : Trần Thị Ngọc Hoa14 Asymmetric Algorithms EncryptDecrypt Data #$ad^&* Data Public keyPrivate key  2 different but related keys are required.  RSA -Rivest, Shamir, and Adelman  ElGamal

Lecturer : Trần Thị Ngọc Hoa15 Hashing Algorithms  Hashing algorithms are used for authentication and integrity assurance for data  They are based on some type of one-way hashing function.  SHA 128 bits output  MD5 160 bits output  Collision : 2 different inputs => the same output  SHA is prefered than MD5

Lecturer : Trần Thị Ngọc Hoa16 Hashing Example

Lecturer : Trần Thị Ngọc Hoa17 Key Exchange Problem  Question : How to get the key from one device to the other ? If the key is sent across an untrusted network, you run the risk of it being sniffed and captured by a hacker. If you phone the technician at the other end, you run the risk of phone tapping.  Answer : Diffie Hellman

Lecturer : Trần Thị Ngọc Hoa18 Diffie Hellman Key Exchange  The Diffe-Hellman key exchange is used for automatic secure key exchange of Symmetrical keys Other types of keys  Algorithm Description Step 1 : A and B pour their favourite drink into the glass Step 2 : A and B pour the same liquid into the glass Step 3 : A and B exchange their own glass.Then pickup the other liquid and mixed with their own one

Lecturer : Trần Thị Ngọc Hoa19 IPSec Protocols  AH Provide  Data integrity  Data authentication  Antireplay protection (optionally) Not provide any form of encryption to the payload of the packet.  ESP Provide payload encryption Provide authentication and integrity

Lecturer : Trần Thị Ngọc Hoa20 Security Mode  Both ESP and AH can operate in two different modes  Tunnel Mode : The entire packet is encrypted then encapsulated with a new, unprotected IP header.  Transport Mode : Default mode The original IP header is reused with the new packet The current IP header has been used in the hashing algorithm and therefore cannot be changed from sender to receiver.

Lecturer : Trần Thị Ngọc Hoa21 Security Associations  A set of policy and key(s) used to protect data before an IPSec tunnel can be created.  Each SA gets a unique 32-bit Security Parameter Index number – SPI – that is sent in every packet pertaining to the specific SA.  The SA keeps track of general information such as the following: Source IP address Destination IP address IPSec protocols used SPI number Encryption and authentication algorithms Key lifetime (sets the amount of time and/or byte count that a key is valid for; the longer the time, the more vulnerable your data is)

Lecturer : Trần Thị Ngọc Hoa22 Internet Key Exchange  Internet Key Exchange (IKE) is used to establish all the information needed – SA – for a tunnel.  2 phases Main mode – IKE Phase 1 Quick mode – IKE Phase 2