ISC Updated SSCP Exam Questions and Answers by fatimah

In a ciphertext-only attack, the attacker has the ciphertext of several messages encrypted with the same encryption algorithm. Its goal is to discover the plaintext of the messages by figuring out the key used in the encryption process. In a known-plaintext attack, the attacker has the plaintext and the ciphertext of one or more messages. In a chosen-ciphertext attack, the attacker can chose the ciphertext to be decrypted and has access to the resulting plaintext.

Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, Chapter 8: Cryptography (page 578).

A certification authority (CA) is a third party entity that issues digital certificates (especially X.509 certificates) and vouches for the binding between the data items in a certificate. An issuing authority could be considered a correct answer, but not the best answer, since it is too generic.

Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.

Kerberos depends on secret keys (symmetric ciphers). Kerberos is 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.

The following answers are incorrect:

It utilizes public key cryptography. Is incorrect because Kerberos depends on secret keys (symmetric ciphers).

It encrypts data after a ticket is granted, but passwords are exchanged in plain text. Is incorrect because the passwords are not exchanged but used for encryption and decryption of the keys.

It is a second party authentication system. Is incorrect because Kerberos is a third party authentication system, you authenticate to the third party (Kerberos) and not the system you are accessing.

References:

MIT http://web.mit.edu/kerberos/

Wikipedi http://en.wikipedia.org/wiki/Kerberos_%28protocol%29

OIG CBK Access Control (pages 181 - 184)

AIOv3 Access Control (pages 151 - 155)

Notice that the question specifically asks what PGP uses to encrypt For this, PGP uses an symmetric key algorithm. PGP then uses an asymmetric key algorithm to encrypt the session key and then send it securely to the receiver. It is an hybrid system where both types of ciphers are being used for different purposes.

Whenever a question talks about the bulk of the data to be sent, Symmetric is always best to choice to use because of the inherent speed within Symmetric Ciphers. Asymmetric ciphers are 100 to 1000 times slower than Symmetric Ciphers.

The other answers are not correct because:

"An asymmetric encryption algorithm" is incorrect because PGP uses a symmetric algorithm to encrypt data.

"A symmetric key distribution system" is incorrect because PGP uses an asymmetric algorithm for the distribution of the session keys used for the bulk of the data.

"An X.509 digital certificate" is incorrect because PGP does not use X.509 digital certificates to encrypt the data, it uses a session key to encrypt the data.

References:

Official ISC2 Guide page: 275

All in One Third Edition page: 664 - 665