8.4 – 8.5 Securing E-mail & Securing TCP connections with SSL

By: Amanda Porter

8.4 Securing E-mail

4 Layers in Protocol Stack •Application Layer

▫Email•Transport Layer

▫SSL Protocol•Network Layer

▫IPSec•Link Layer

▫IEEE 802.11

8.4 Securing E-mail

Why have multiple-layer security?

•To provide user level security

• It is easier to deploy security services at higher layers in protocol stack

8.4 Securing E-mail

4 Security Features

•Confidentiality

•Sender Authentication

•Message Integrity

•Receiver Authentication

8.4 Securing E-mail

Confidentiality

•Public Key Cryptography

▫RSA

•Symmetric Key Technology

▫DES or AES

8.4 Securing E-mail

Sender Authentication & Message

Integrity

•Without Confidentiality

▫Digital Signatures and Message Digests

8.4 Securing E-mail

Sender Authentication & Message

Integrity

•With Confidentiality

8.4 Securing E-mail

Pretty Good Privacy (PGP)---BEGIN PGP SIGNED MESSAGE--- Hash: SHA1 Bob: My husband is out of town tonight.Passionately yours, Alice ---BEGIN PGP SIGNATURE--- Version: PGP 5.0 Charset: noconv yhHJRHhGJGhgg/12EpJ+lo8gE4vB3mqJhFEvZP9t6n7G6m5Gw2 ---END PGP SIGNATURE---

---BEGIN PGP MESSAGE---Version: PGP 5.0u4g9fh0KJF03hjdoe./jehfiwoefwehg032rskjclnvbiol-----END PGP MESSAGE

8.5 Securing TCP Connections: SSLSSL

•Secure Sockets Layer

▫Enhanced version of TCP

•Transport Layer Security

▫Slightly modified version of SSL (version 3)

•Https

8.5 Securing TCP Connections: SSLWhy SSL?

•Provides confidentiality

•Provides data integrity

•Provides server authentication

8.5 Securing TCP Connections: SSLThree Phases

•Handshake

•Key Derivation

•Data Transfer

(Connection Closure)

8.5 Securing TCP Connections: SSLSSL Handshake

•Server authentication

▫Master Secret (MS)

▫Encrypted Master Secret (EMS)

8.5 Securing TCP Connections: SSLSSL Key Derivation

•Generate Four Keys:

▫EB = encryption

▫MB = MAC

▫EA = encryption

▫MA = MAC

8.5 Securing TCP Connections: SSLSSL Data Transfer

•Break data stream into records:

Data MACVersion LengthType

Encrypted with EB

8.5 Securing TCP Connections: SSLReal SSL

•Server authentication

•Negotiation: agree on crypto

algorithms

•Establish keys

•Client authentication (optional)

8.5 Securing TCP Connections: SSLClosing

Connection

•TCP FIN

•Type field

Bibliography• [1] J. Kurose and K. Ross, Computer Networking: A top-down

approach, 5th edition. New York: Pearson Education, Inc., 2010.• [2] M.S.Bhiogade, “Secure Socket Layer”, in InSITE - “Where

Parallels Intersect,” June 2002, pp. 85-90.• [3]A. Weaver, “How Things Work Secure Sockets Layer,” in Computer

– Innovative Technology for Computing Professionals, April 2006.• [4] R. Bazile and O. Wong, “Pretty Good Privacy Network Security and

Cryptography, CS682,” November 4, 2002.• [5] D.V. Bhatt, S. Schulze, G.P. Hancke, L. Horvath, “Secure Internet

access to gateway using secure socket layer,” in Virtual Environments, Human-Computer Interfaces and Measurement Systems, July 2003, pp. 157- 162.

• [6] S. Garfinkel and G. Spafford, Web Security and Commerce. Sebastopol, CA : O'Reilly & Associates, Inc. , 1997.

• [7] A. Levi and Ç. K. Koç, “Risks in Email Security,” in Inside Risks, 2001.

• [8] M. Sunner , “Email Security,” in Network Security, Volume 2005, Issue 12, December 2005, pp. 4-7.