IP Securty 1. Overview 2. Architecture 3. Authentication Header 4. Encapsulating Security Payload 5. Combining security Associations 6. Internet Key Exchange. Web Security: 1. Web Security Considerations, 2. Secure Sockets Layer 3. Transport Layer Security, 4. Electronic Payment

IP Security have a range of application specific security mechanisms ◦ eg. S/MIME, PGP, Kerberos, SSL/HTTPS however there are security concerns that cut across protocol layers would like security implemented by the network for all applications

IPSec general IP Security mechanisms provides ◦ authentication ◦ confidentiality ◦ key management applicable to use over LANs, across public & private WANs, & for the Internet

IPSec Uses

Benefits of IPSec in a firewall/router provides strong security to all traffic crossing the perimeter in a firewall/router is resistant to bypass is below transport layer, hence transparent to applications can be transparent to end users can provide security for individual users secures routing architecture

IP Security Architecture specification is quite complex defined in numerous RFC’s ◦ incl. RFC 2401/2402/2406/2408 ◦ many others, grouped by category mandatory in IPv6, optional in IPv4 have two security header extensions: ◦ Authentication Header (AH) ◦ Encapsulating Security Payload (ESP)

IPSec Services Access control Connectionless integrity Data origin authentication Rejection of replayed packets ◦ a form of partial sequence integrity Confidentiality (encryption) Limited traffic flow confidentiality

Security Associations a one-way relationship between sender & receiver that affords security for traffic flow defined by 3 parameters: ◦ Security Parameters Index (SPI) ◦ IP Destination Address ◦ Security Protocol Identifier has a number of other parameters ◦ seq no, AH & EH info, lifetime etc have a database of Security Associations

Authentication Header (AH) provides support for data integrity & authentication of IP packets ◦ end system/router can authenticate user/app ◦ prevents address spoofing attacks by tracking sequence numbers based on use of a MAC ◦ HMAC-MD5-96 or HMAC-SHA-1-96 parties must share a secret key

Authentication Header

Transport & Tunnel Modes

Encapsulating Security Payload (ESP) provides message content confidentiality & limited traffic flow confidentiality can optionally provide the same authentication services as AH supports range of ciphers, modes, padding ◦ incl. DES, Triple-DES, RC5, IDEA, CAST etc ◦ CBC & other modes ◦ padding needed to fill blocksize, fields, for traffic flow

Encapsulating Security Payload

Transport vs Tunnel Mode ESP transport mode is used to encrypt & optionally authenticate IP data ◦ data protected but header left in clear ◦ can do traffic analysis but is efficient ◦ good for ESP host to host traffic tunnel mode encrypts entire IP packet ◦ add new header for next hop ◦ good for VPNs, gateway to gateway security

Combining Security Associations SA’s can implement either AH or ESP to implement both need to combine SA’s ◦ form a security association bundle ◦ may terminate at different or same endpoints ◦ combined by  transport adjacency  iterated tunneling issue of authentication & encryption order

Combining Security Associations

Key Management handles key generation & distribution typically need 2 pairs of keys ◦ 2 per direction for AH & ESP manual key management ◦ sysadmin manually configures every system automated key management ◦ automated system for on demand creation of keys for SA’s in large systems ◦ has Oakley & ISAKMP elements

Oakley a key exchange protocol based on Diffie-Hellman key exchange adds features to address weaknesses ◦ cookies, groups (global params), nonces, DH key exchange with authentication can use arithmetic in prime fields or elliptic curve fields

ISAKMP Internet Security Association and Key Management Protocol provides framework for key management defines procedures and packet formats to establish, negotiate, modify, & delete SAs independent of key exchange protocol, encryption alg, & authentication method

ISAKMP

ISAKMP Payloads & Exchanges have a number of ISAKMP payload types: ◦ Security, Proposal, Transform, Key, Identification, Certificate, Certificate, Hash, Signature, Nonce, Notification, Delete ISAKMP has framework for 5 types of message exchanges: ◦ base, identity protection, authentication only, aggressive, informational

Web Security Web now widely used by business, government, individuals but Internet & Web are vulnerable have a variety of threats ◦ integrity ◦ confidentiality ◦ denial of service ◦ authentication need added security mechanisms

SSL (Secure Socket Layer) transport layer security service originally developed by Netscape version 3 designed with public input subsequently became Internet standard known as TLS (Transport Layer Security) uses TCP to provide a reliable end-to-end service SSL has two layers of protocols

Where SSL Fits HTTP SMTP POP HTTPS SSMTP SPOP Secure Sockets Layer Transport Network Link

Uses Public Key Scheme Each client-server pair uses ◦ 2 public keys  one for client (browser)  created when browser is installed on client machine  one for server (http server)  created when server is installed on server hardware ◦ 2 private keys  one for client browser  one for server (http server)

SSL Architecture

SSL session ◦ an association between client & server ◦ created by the Handshake Protocol ◦ define a set of cryptographic parameters ◦ may be shared by multiple SSL connections SSL connection ◦ a transient, peer-to-peer, communications link ◦ associated with 1 SSL session

SSL Record Protocol confidentiality ◦ using symmetric encryption with a shared secret key defined by Handshake Protocol ◦ IDEA, RC2-40, DES-40, DES, 3DES, Fortezza, RC4-40, RC4-128 ◦ message is compressed before encryption message integrity ◦ using a MAC (Message Authentication Code) created using a shared secret key and a short message

SSL Change Cipher Spec Protocol one of 3 SSL specific protocols which use the SSL Record protocol a single message causes pending state to become current hence updating the cipher suite in use

SSL Alert Protocol conveys SSL-related alerts to peer entity severity  warning or fatal specific alert  unexpected message, bad record mac, decompression failure, handshake failure, illegal parameter  close notify, no certificate, bad certificate, unsupported certificate, certificate revoked, certificate expired, certificate unknown compressed & encrypted like all SSL data

SSL Handshake Protocol allows server & client to: ◦ authenticate each other ◦ to negotiate encryption & MAC algorithms ◦ to negotiate cryptographic keys to be used comprises a series of messages in phases ◦ Establish Security Capabilities ◦ Server Authentication and Key Exchange ◦ Client Authentication and Key Exchange ◦ Finish

SSL Handshake Protocol

TLS (Transport Layer Security) IETF standard RFC 2246 similar to SSLv3 with minor differences ◦ in record format version number ◦ uses HMAC for MAC ◦ a pseudo-random function expands secrets ◦ has additional alert codes ◦ some changes in supported ciphers ◦ changes in certificate negotiations ◦ changes in use of padding

Secure Electronic Transactions (SET) open encryption & security specification to protect Internet credit card transactions developed in 1996 by Mastercard, Visa etc not a payment system, rather a set of security protocols & formats ◦ secure communications amongst parties ◦ trust from use of X.509v3 certificates ◦ privacy by restricted info to those who need it

SET Components

SET Transaction 1. customer opens account 2. customer receives a certificate 3. merchants have their own certificates 4. customer places an order 5. merchant is verified 6. order and payment are sent 7. merchant requests payment authorization 8. merchant confirms order 9. merchant provides goods or service 10. merchant requests payment

Dual Signature customer creates dual messages ◦ order information (OI) for merchant ◦ payment information (PI) for bank neither party needs details of other but must know they are linked use a dual signature for this ◦ signed concatenated hashes of OI & PI

Purchase Request – Customer

Purchase Request – Merchant

1. verifies cardholder certificates using CA sigs 2. verifies dual signature using customer's public signature key to ensure order has not been tampered with in transit & that it was signed using cardholder's private signature key 3. processes order and forwards the payment information to the payment gateway for authorization (described later) 4. sends a purchase response to cardholder

Payment Gateway Authorization 1. verifies all certificates 2. decrypts digital envelope of authorization block to obtain symmetric key & then decrypts authorization block 3. verifies merchant's signature on authorization block 4. decrypts digital envelope of payment block to obtain symmetric key & then decrypts payment block 5. verifies dual signature on payment block 6. verifies that transaction ID received from merchant matches that in PI received (indirectly) from customer 7. requests & receives an authorization from issuer 8. sends authorization response back to merchant

Payment Capture merchant sends payment gateway a payment capture request gateway checks request then causes funds to be transferred to merchants account notifies merchant using capture response