1. Security Outline Encryption Algorithms Authentication Protocols Message Integrity Protocols Key Distribution Firewalls

2. Overview Cryptography functions –Secret key (e.g., DES) –Public key (e.g., RSA) –Message digest (e.g., MD5) Security services –Privacy (Secrecy): preventing unauthorized release of information –Authentication: verifying identity of the remote participant –Integrity: making sure message has not been altered Security Cryptography algorithms Public key (e.g., RSA) Secret key (e.g., DES) Message digest (e.g., MD5) Security services AuthenticationPrivacyMessage integrity

3. Secret Key Plaintex t Encrypt with secret key Ciphertext Plaintext Decrypt with secret key Data Encryption Standard (DES) is a data encryption method applying a 56-bit private (secret) key to encrypt each 64-bit block of data.

4. Cipher Transition cipher reorders the letters without disguising them. –select a key with no repeated letters. key = M E G A B U C K 7 4 5 1 2 8 3 6 --------------- p l e a s e t r a n s f e r o n e h u n d r e d  afnsedtoelnhesurndpaeerr plain text  cipher text

5. Example Pretty Good Privacy (PGP) is a popular program used to encrypt and decrypt e-mail over the Internet. Transport Layer Security (TLS) is a protocol that ensures privacy between communicating applications and their users on the Internet. The Secure Sockets Layer (SSL) is a commonly-used protocol for managing the security of a message transmission on the Internet. HTTPS (Hypertext Transfer Protocol over Secure Socket Layer, or HTTP over SSL) is a Web protocol developed by Netscape and built into its browser that encrypts and decrypts user page requests as well as the pages that are returned by the Web server.

6. Public Key Plaintext Encrypt with public key Ciphertext Plaintext Decrypt with private key RSA is an Internet encryption and authentication system that uses an algorithm developed by Ron Rivest, Adi Shamir, and Leonard Adleman which uses a public key to encrypt and a private key to decrypt

7. Firewalls A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. Rest of the InternetLocal siteFirewall