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Web Security

Web Security. Web Security Introduction. Need for security on the Transport Control Protocol (TCP) Layer Uses Secure Socket Layer (SSL) and Internet standard SSL called Transport Layer Service Allows TCP users to indentify security mechanisms

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Web Security

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  1. Web Security

  2. Web Security Introduction • Need for security on the Transport Control Protocol (TCP) Layer • Uses Secure Socket Layer (SSL) and Internet standard SSL called Transport Layer Service • Allows TCP users to indentify security mechanisms • Particularly concerted with E – commerce security: Secure Electronic Transaction (SET)

  3. Web Security Considerations • Room for nearly all levels of security in the Web • E.g. previous considerations • Nevertheless: Web presents unique challenges • All communication two way thus doubling the opportunity for attack • Web integrated into business: high losses if security compromised • Security flaws in complex software • Web Servers may provide access to local intranet • Users not aware of security risks

  4. Threats Classifications

  5. Web Security Approaches • Different ways of implementing security • Similar in services and (to an extent) mechanisms • Differ with respect to scope and location with TCP/IP stack • Simple security: Use IP Security! IPSec runs over TCP • Another solution: Run security just above TCP, below IP • Basis of SSL and TLS • Choice: Make SSL/TLS transparent or integrate into applications? (advantage: tailored to needs, disadvantage: complexity)

  6. SSL and TLS • Current version is SSL v3. TLS is essentially SSLv3.1 • Not a “successor” exactly, just a different standard • SSL Architecture • Make TCP reliable/secure • Higher level protocols operate (HTTP for instance) on SSL • SSL uses three protocols: Handshake Protocol, Change Cipher Spec Protocol, Alter Protocol • Also a special “record” protocol • Used in management of SSL exchanges

  7. 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

  8. SSL Architecture

  9. SSL Architecture • SSL connection • A transient, peer-to-peer, communications link • Associated with 1 SSL session • 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

  10. Session and Connection States • Session state has following parameters • Session Identifier, Peer certificate (X509, etc) • Compression Method • Cipher spec (data encryption) and hash • Master secret • Is resumable? • Connection state: • Server and client randomness • Keys: Server/Client MAC, Server/Client Write • Initialization vectors • Sequence numbers

  11. SSL Record Protocol Services • Message integrity • Using a MAC with shared secret key • Similar to HMAC but with different padding • Confidentiality • Using symmetric encryption with a shared secret key defined by handshake protocol • AES, IDEA, RC2-40, DES-40, DES, 3DES, fortezza, RC4-40, RC4-128 • Message is compressed before encryption

  12. SSL Record Appearance

  13. SSL Record Protocol Operation

  14. 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

  15. SSL Alert Protocol • Conveys ssl-related alerts to peer entity • Severity • Warning or fatal • Specific alert • Fatal: unexpected message, bad record mac, decompression failure, handshake failure, illegal parameter • Warning: close notify, no certificate, bad certificate, unsupported certificate, certificate revoked, certificate expired, certificate unknown • Compressed & encrypted like all SSL data

  16. 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

  17. SSL Handshake Protocol

  18. 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 types & negotiations • Changes in crypto computations & padding

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