Securing Insecure Networks SSL/TLS & IPSec

4-1: Cryptographic System Copyright Pearson Prentice-Hall

Cryptographic System Standards  Transmission across Un-trusted Networks  Internet, Wireless LAN’s, etc.  Companies will (should) apply Cryptographic Systems  Virtual Private Network (VPN)  SSL/TLS  Secure Socket Layer/Transport Layer Security  Non-Transparent, doesn’t automatically protect application messages.  Only messages from applications that are SSL/TSL aware  Web Browsers/Web Servers; Many  But there’s a problem But there’s a problem  IPsec  Operates on the Internet layer  Everything in IP packet data file is protected  Transparent protection – applications and transport layer are protected (see Module A) Copyright Pearson Prentice-Hall LayerHybrid TCP/IP-OSI Application InternetTransport (TCP, UDP) IP Single NetworkData Link Physical

4-2: Virtual Private Networks (VPNs) Copyright Pearson Prentice-Hall

Host-to-Host VPNs  Connect one Client to one Server Copyright Pearson Prentice-Hall

4-3: Host-to-Host SSL/TLS VPN Copyright Pearson Prentice-Hall

Remote Access VPNs  Connects a single Client to a Network  Connection is to a VPN Gateway  Used for Authentication and Access Control  Depending on Access Authorization connection can be to multiple computers on the network.  Uses SSL/TSL between Browser and Gateway  The Gateway is a WebServer to SSL/TSL  SSL/TSL protects messages between client and Gateway  Gateway authenticates with the client via Public Key Authentication Copyright Pearson Prentice-Hall

Types of Remote Access Connections  Web server  Database server  Gateway translates browser requests to Queries to database  Gateway translates database response to web pages “webifies”  Router  Connection to subnet of network Copyright Pearson Prentice-Hall

4-5: SSL/TLS and Remote Access VPN Using a Gateway Copyright Pearson Prentice-Hall

4-4: SSL/TLS Handshaking Phase Copyright Pearson Prentice-Hall StepSenderName of Message Semantics (Meaning) 1ClientClient HelloClient requests secure connection. Client lists cipher suites it supports. 2ServerServer HelloServer indicates willingness to proceed. Selects a cipher suite to use in the session. 3ServerCertificateServer sends its digital certificate containing its public key. (Client should check the certificate’s validity.) 4ServerServerHelloDoneServer indicates that its part in the initial introduction is finished. Stage 1 Stage 2 & 3 ???

4-4: SSL/TLS Handshaking Phase Copyright Pearson Prentice-Hall StepSenderName of Message Semantics (Meaning) 5ClientClientKey Exchange Client generates a random symmetric session key. Encrypts it with the server’s public key. It sends this encrypted key to the server. Only the server can decrypt the key, using the server’s own private key. The server decrypts the session key. Both sides now have the session key. 6ClientChangeCipher Spec* Client changes selected cipher suite from pending to active. 7ClientFinishClient indicates that its part in the initial introduction is finished. *Not cipher suite. Key Exchange using public key encryption for confidentiality Key Exchange using public key encryption for confidentiality Stage 2 & 3

4-4: SSL/TLS Handshaking Phase Copyright Pearson Prentice-Hall StepSenderName of MessageSemantics (Meaning) 8ServerChangeCipherSpec*Server changes selected cipher suite from pending to active. 9ServerFinishServer indicates that its role in selecting options is finished. 10Ongoing communication stage begins *Not cipher suite.

Copyright Pearson Prentice-Hall

Site-to-Site VPNs  Protects all traffic between two sites  VPN Gateway on both ends of transmission  VPN Gateway’s encrypt/decrypt messages Copyright Pearson Prentice-Hall

IPsec Modes  Transport (Host-to-Host)  Protects messages from host-to-host  Over the internet and Internet  Requires installing IPsec on each client/server (not built into browser)  Costly  Eliminates ability of Firewall to filter content as it is encrypted  Tunnel (Site-to-Site)  Protects messages between VPN Gateways over the Internet  Less Costly than Transport  Firewall can filter content Copyright Pearson Prentice-Hall

IPsec Operation: Transport Mode Copyright Pearson Prentice-Hall End-to-End Security (Good) 1. End-to-End Security (Good) 2. Security in Site Network (Good) 2. Security in Site Network (Good) 3. Setup Cost On Each Host (Costly) 3. Setup Cost On Each Host (Costly)

IPsec Operation: Tunnel Mode Copyright Pearson Prentice-Hall No Security in Site Network (Bad) 2. No Security in Site Network (Bad) 3. No Setup Cost On Each Host (Good) 3. No Setup Cost On Each Host (Good)

4-8: Comparing IPsec Transport and Tunnel Modes Copyright Pearson Prentice-Hall CharacteristicTransport ModeTunnel Mode Uses an IPsec VPN Gateway? NoYes Cryptographic Protection All the way from the source host to the destination host, including the Internet and the two site networks. Only over the Internet between the IPsec gateways. Not within the two site networks. Setup CostsHigh. Setup requires the creation of a digital certificate for each client and significant configuration work. Low. Only the IPsec gateways must implement IPsec, so only they need digital certificates and need to be configured.

4-8: Comparing IPsec Transport and Tunnel Modes Copyright Pearson Prentice-Hall CharacteristicTransport ModeTunnel Mode Firewall FriendlinessBad. A firewall at the border to a site cannot filter packets because the content is encrypted. Good. Each packet is decrypted by the IPsec gateway. A border firewall after the IPsec gateway can filter the decrypted packet. The “Bottom Line”End-to-end security at high cost. Low cost and protects the packet over the most dangerous part of its journey.

4-6: IP Security (IPsec) versus SSL/TLS Copyright Pearson Prentice-Hall SSL/TLSIPsec Cryptographic security standardYes Cryptographic security protectionsGoodGold Standard Supports central managementNoYes Complexity and expenseLowerHigher Layer of operationTransportInternet Transparently protects all higher-layer traffic NoYes Works with IPv4 and IPv6NAYes Modes of operationNATransport, Tunnel

4-9: IPsec Security Associations Copyright Pearson Prentice-Hall Kind of like a cipher suite