vpn

Virtual Private Networks : 

Virtual Private Networks Fred Baker

What is a VPN : 

What is a VPN Public networks are used to move information between trusted network segments using shared facilities like frame relay or atm A VIRTUAL Private Network replaces all of the above utilizing the public Internet Performance and availability depend on your ISP and the Internet

Why? : 

Why?

HomeNet to the office. : 

HomeNet to the office.

VPN Types : 

VPN Types

VPN Implementations : 

VPN Implementations

VPN as your Intranet : 

VPN as your Intranet

What a VPN needs : 

What a VPN needs VPNs must be encrypted so no one can read it VPNs must be authenticated No one outside the VPN can alter the VPN All parties to the VPN must agree on the security properties

VPN Components : 

VPN Components

Parts of a VPN : 

Parts of a VPN

VPN works via crypto/Encapsulation : 

VPN works via crypto/Encapsulation

Encryption and Decryption : 

Encryption and Decryption Clear-Text Clear-Text Cipher Text 8vyaleh31&d ktu.dtrw8743 $Fie*nP093h

Basic Crypto – Keys are key : 

Basic Crypto – Keys are key

2 Kinds Key Systems : 

2 Kinds Key Systems

Symmetric Key Algorithms : 

Symmetric Key Algorithms DES—56-bit key Triple-DES—encrypt, decrypt, encrypt, using either two or three 56-bit keys IDEA—128-bit key Blowfish—variable-length key, up to 448 bits

Public Key Encryption Example : 

Public Key Encryption Example Message Alice Bob Encrypted Message Message Bob’s Public Key Bob’s Private Key Decrypt Alice wants to send Bob encrypted data Alice gets Bob’s public key Alice encrypts the data with Bob’s public key Alice sends the encrypted data to Bob Bob decrypts the data with his private key Encryption

PKI vs Symmetric Key : 

PKI vs Symmetric Key PKI easier as you don’t have to manage keys on a per user basis But MUCH more compute intensive (up to 1000 times faster) Many systems do a combination I.e. PGP Use PKI to send a symmetric key Then use the symmetric key to crypto the data

Using Crypto in real life : 

Using Crypto in real life

PKI to send Private Keys : 

PKI to send Private Keys

PKI Certs a way to authenticate : 

PKI Certs a way to authenticate

Prove the user cert Certificates of authority : 

Prove the user cert Certificates of authority

Digital Signature to verify data not changed in transit : 

Digital Signature to verify data not changed in transit

PKI the full picture : 

PKI the full picture

Where you do Crypto : 

Where you do Crypto

Technologies : 

Technologies

Application Layer: SSL : 

Application Layer: SSL

Transport Layer: IPSEC : 

Transport Layer: IPSEC A standard is composed of: Diffie-Huffman key exchange PKI for the DH exchanges DES and other bulk encryption Hash to authenticate packets Digital Certificates to validate keys

Transport Layer: IPSEC VPNs3 parts : 

Transport Layer: IPSEC VPNs3 parts

Tunnel vs Transport : 

Tunnel vs Transport Transport Implemented by the end point systems Real address to real address Cannot ‘go through’ other networks Tunnel Encapsulation of the original IP packet in another packet Can ‘go through’ other networks End systems need not support this Often PC to a box on the ‘inside’

Diffie-Hellman Key Exchange (1976) : 

Diffie-Hellman Key Exchange (1976) By openly exchanging non-secret numbers, two people can compute a unique shared secret number known only to them

Modular Exponentiation : 

Modular Exponentiation Generator, g Modulus (prime), p Y = gX mod p 2^237276162930753723 mod 79927397984597926572651 Both g and p Are Shared and Well-Known

Diffie-HellmanPublic Key Exchange : 

Diffie-HellmanPublic Key Exchange Private Value, XA Public Value, YA Private Value, XB Public Value, YB (shared secret) Alice Bob YB mod p = g mod p = YA mod p XB XA XB YA YB XA

Security Association is the agreement on how to secure : 

Security Association is the agreement on how to secure

create the ISAKMP SA (Internet Security Association Key Management Protocol) : 

create the ISAKMP SA (Internet Security Association Key Management Protocol)

IPSEC Key Exchange (IKE) : 

IPSEC Key Exchange (IKE)

IKE allows scale as I do not need to hard code passwords for each pair : 

IKE allows scale as I do not need to hard code passwords for each pair

Link Layer: L2TP for VPDN (Vir Pvt Dial Net) : 

Link Layer: L2TP for VPDN (Vir Pvt Dial Net)

PPTP: Free from Microsoft : 

PPTP: Free from Microsoft

PPTP: Security : 

PPTP: Security

VPN Comparisons : 

VPN Comparisons

So why have a private network: QOS not fully cooked : 

So why have a private network: QOS not fully cooked Very dependent on your ISP Real hard to do across ISPs So no guarantee of performance

Other Issues : 

Other Issues

Like Nat : 

Like Nat

Wireless: a new big driver, WAS (Work At Starbucks) : 

Wireless: a new big driver, WAS (Work At Starbucks)

Many security protocols, depends on deployer : 

Many security protocols, depends on deployer

VPN means I don’t care how you connect : 

VPN means I don’t care how you connect

Example : 

Example

So what could be wrong? : 

So what could be wrong? VPN clients hit the network stack May not play well with personal firewalls Or other software May not need full access to the target network just encrypted access

One answer: clientless VPN : 

One answer: clientless VPN Use SSL as the transport protocol to an appliance Can add NT authentication to the appliance Clientless mode: Use web enabled applications over the Internet, the appliance SSLifies web sites Java Applet: Use an downloadable applet to send traffic over SSL, get more support for applications. Can work well if you want to have encrypted web based apps without redoing the application to use SSL you need certs and have to change EVERY link to HTTPs Also big hit on the server cpu

Summary: VPNs : 

Summary: VPNs Very big in the work access space Exploit High speed Wireless in the office public ‘hot spots’ like Borders Replaces direct dial into the work network Replace dedicated Business partners May replace the corporate WAN