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2. Objectives Understand the use of encryption and hashing technologies and PKI Identify the use of protocols to configure a remote access server or VPN 5.2 Remote Access Services 396

3. Encryption o Scramble a message (plaintext) in such a way (ciphertext) that it can only be unscrambled with the key Confidentiality / privacy / integrity o Users cannot read the messages without the key o Users should be confident the message is as the sender composed it Authentication o Possessing the key might demonstrate that only the holder could have composed a message Digital Security 5.2 Remote Access Services 396

4. The same key is used both to encrypt and decrypt messages Referred to as secret key or single key Distribution of the key is difficult Symmetric encryption is not processor intensive – suitable for encrypting and decrypting large files quickly DES, AES, RC (Rivest Cipher), IDEA, Blowfish/Twofish, and CAST Key size Symmetric Encryption 5.2 Remote Access Services 396

5. Uses two linked keys (a key pair) – one to encrypt and the other to decrypt Referred as public key cryptography Public key is distributed to anyone Private key is kept secret by the owner Processor-intensive – only works well on short messages Often used for authentication and exchanging symmetric encryption keys securely Asymmetric Encryption 5.2 Remote Access Services 397

6. Means of vouching for a subject’s identity A Certificate Authority (CA) issues a Digital Certificates to a web server computer whose identity they have validated The digital certificate contains the server’s public key and is digitally signed by the CA Clients can use the public key to communicate with the server securely Clients can trust that the server is genuine if they trust the CA Clients are installed with the root certificates of CAs that they trust Public Key Infrastructure (PKI) 5.2 Remote Access Services 397

7. Cryptographic Hashes A hash creates a shorter fixed length digest from an original message A cryptographic creates a one-way digest – the original message cannot be recovered from the digest Secure Hash Algorithm (SHA-1 and SHA-2) Message Digest (MD5) 5.2 Remote Access Services 398

8. Remote Access Services (RAS) Tunneling / encapsulation Remote Access Services 5.2 Remote Access Services 398

9. Virtual Private Networks Host-to-site Site-to-site Host-to-host 5.2 Remote Access Services 399

10. Point-to-Point Protocol (PPP) PPP over Ethernet (PPPoE) Point-to-Point Tunneling Protocol (PPTP) Layer 2 Tunneling Protocol (L2TP) IPsec Secure Sockets Layer (SSL) / Transport Layer Security (TLS) Remote Access Protocols 5.2 Remote Access Services 400

11. Remote Access Servers Dial-up o Configure user rights o Callback o Authentication o Encryption VPN RAS 5.2 Remote Access Services 401

12. RADIUS and TACACS+ 5.2 Remote Access Services 401

13. PAP and CHAP Password Authentication Protocol (PAP) Challenge Handshake Authentication Protocol (CHAP) Standard authentication protocol for PPP Three-way handshake o Challenge o Response o Accept Handshake is repeated during the session to prevent replay MS-CHAP 5.2 Remote Access Services 402

14. EAP / IEEE 802.1X Extensible Authentication Protocol (EAP) Designed to provide for interoperable security devices and software o Supplicant o Authenticator o Authentication Server EAP-TLS (Transport Layer Security) Protected EAP (PEAP) EAP-TTLS (Tunneled Transport Layer Security) 5.2 Remote Access Services 403

15. Review Understand the use of encryption and hashing technologies and PKI Identify the use of protocols to configure a remote access server or VPN 5.2 Remote Access Services 405