Section: Cryptography
Explanation/Reference:
Kerberos depends on Secret Keys or Symmetric Key cryptography.
Kerberos a third party authentication protocol. It was designed and developed in the mid 1980's by MIT. It is considered open source but is copyrighted and owned by MIT. It relies on the user's secret keys. The password is used to encrypt and decrypt the keys.
This question asked specifically about encryption methods. Encryption methods can be SYMMETRIC (or secret key) in which encryption and decryption keys are the same, or ASYMMETRIC (aka 'Public Key') in which encryption and decryption keys differ.
'Public Key' methods must be asymmetric, to the extent that the decryption key CANNOT be easily derived from the encryption key. Symmetric keys, however, usually encrypt more efficiently, so they lend themselves to encrypting large amounts of data. Asymmetric encryption is often limited to ONLY encrypting a symmetric key and other information that is needed in order to decrypt a data stream, and the remainder of the encrypted data uses the symmetric key method for performance reasons. This does not in any way diminish the security nor the ability to use a public key to encrypt the data, since the symmetric key method is likely to be even MORE secure than the asymmetric method.
For symmetric key ciphers, there are basically two types: BLOCK CIPHERS, in which a fixed length block is encrypted, and STREAM CIPHERS, in which the data is encrypted one 'data unit' (typically 1 byte) at a time, in the same order it was received in.
The following answers are incorrect:
Public Key cryptography. Is incorrect because Kerberos depends on Secret Keys or Symmetric Key cryptography and not Public Key or Asymmetric Key cryptography.
El Gamal cryptography. Is incorrect because El Gamal is an Asymmetric Key encryption algorithm.
Blowfish cryptography. Is incorrect because Blowfish is a Symmetric Key encryption algorithm.
References:
OIG CBK Access Control (pages 181 - 184)
AIOv3 Access Control (pages 151 - 155)
Wikipedia http://en.wikipedia.org/wiki/Blowfish_%28cipher%29 ; http://en.wikipedia.org/wiki/El_Gamal
http://www.mrp3.com/encrypt.html

Explanation/Reference:
The CIA acronym stands for Confidentiality, Integrity and Availability.
"Confidentiality, Integrity and Entity (CIE)" is incorrect. "Entity" is not part of the telecommunications domain definition.
"Confidentiality, Integrity and Authenticity (CIA)" is incorrect. While authenticity is included in the telecommunications domain, CIA is the acronym for confidentiality, integrity and availability.
"Confidentiality, Integrity, and Liability (CIL)" is incorrect. Liability is not part of the telecommunications domain definition.
References:
CBK, pp. 407 - 408

Firewall rules can be used to enable access for traffic to specific ports or services. "Service numbers" is rather stilted English but you may encounter these types of wordings on the actual exam -- don't let them confuse you.
"Only unauthorized application port or service numbers" is incorrect. Unauthorized ports/services would be blocked in a properly installed firewall rather than permitting access.
"Only authorized application port or ex-service numbers" is incorrect. "Ex-service" numbers is a nonsense term meant to distract you.
"Only authorized application port or service integers." While service numbers are in fact integers, the more usual (and therefore better) answer is either service or "service number."
References
CBK, p. 464 AIO3, pp. 482 - 484

Explanation/Reference:
RFC 2828 (Internet Security Glossary) defines Simple Key Management for Internet Protocols (SKIP) as:
A key distribution protocol that uses hybrid encryption to convey session keys that are used to encrypt data in IP packets.
SKIP is an hybrid Key distribution protocol similar to SSL, except that it establishes a long-term key once, and then requires no prior communication in order to establish or exchange keys on a session-by-session basis. Therefore, no connection setup overhead exists and new keys values are not continually generated.
SKIP uses the knowledge of its own secret key or private component and the destination's public component to calculate a unique key that can only be used between them.
IKE stand for Internet Key Exchange, it makes use of ISAKMP and OAKLEY internally.
Internet Key Exchange (IKE or IKEv2) is the protocol used to set up a security association (SA) in the IPsec protocol suite. IKE builds upon the Oakley protocol and ISAKMP. IKE uses X.509 certificates for authentication and a Diffie-Hellman key exchange to set up a shared session secret from which cryptographic keys are derived.
The following are incorrect answers:
ISAKMP is an Internet IPsec protocol to negotiate, establish, modify, and delete security associations, and to exchange key generation and authentication data, independent of the details of any specific key generation technique, key establishment protocol, encryption algorithm, or authentication mechanism.
IKE is an Internet, IPsec, key-establishment protocol (partly based on OAKLEY) that is intended for putting in place authenticated keying material for use with ISAKMP and for other security associations, such as in AH and ESP.
IPsec Key exchange (IKE) is only a detracto.
Reference(s) used for this question:
SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.
and
http://en.wikipedia.org/wiki/Simple_Key-Management_for_Internet_Protocol and
http://en.wikipedia.org/wiki/Simple_Key-Management_for_Internet_Protocol

Section: Network and Telecommunications
Explanation/Reference:
L2TP and PPTP were both designed for individual client to server connections; they enable only a single point- to-point connection per session. Dial-up VPNs use L2TP often. Both L2TP and PPTP operate at the data link layer (layer 2) of the OSI model. PPTP uses native PPP authentication and encryption services and L2TP is a combination of PPTP and Layer 2 Forwarding protocol (L2F).
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
95).