212-81 Online Practice Questions and Answers

Correct Answer: A

IDEA https://en.wikipedia.org/wiki/International_Data_Encryption_Algorithm In cryptography, the International Data Encryption Algorithm (IDEA), originally called Improved Proposed Encryption Standard (IPES), is a symmetric-key block cipher designed by James Massey of ETH Zurich and Xuejia Lai and was first described in 1991. The algorithm was intended as a replacement for the Data Encryption Standard (DES). IDEA is a minor revision of an earlier cipher Proposed Encryption Standard (PES). The cipher was designed under a research contract with the Hasler Foundation, which became part of Ascom-Tech AG. The cipher was patented in a number of countries but was freely available for noncommercial use. The name "IDEA" is also a trademark. The last patents expired in 2012, and IDEA is now patent-free and thus completely free for all uses. IDEA was used in Pretty Good Privacy (PGP) v2.0 and was incorporated after the original cipher used in v1.0, BassOmatic, was found to be insecure. IDEA is an optional algorithm in the OpenPGP standard.

Correct Answer: A

Kasiski Method https://en.wikipedia.org/wiki/Kasiski_examination In cryptanalysis, Kasiski examination (also referred to as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigen鑢e cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846.

Correct Answer: B

Substitution

https://en.wikipedia.org/wiki/Substitution_cipher

In cryptography, a substitution cipher is a method of encrypting by which units of plaintext are replaced with ciphertext, according to a fixed system; the "units" may be single letters (the most common), pairs of letters, triplets of letters,

mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution.

Correct Answer: B

Elliptic Curve

https://en.wikipedia.org/wiki/Elliptic-curve_cryptography For current cryptographic purposes, an elliptic curve is a plane curve over a finite field (rather than the real numbers) which consists of the points satisfying the equation:

Correct Answer: B

The ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_feedback_(CFB) The cipher feedback (CFB) mode, a close relative of CBC, makes a block cipher into a self- synchronizing stream cipher.

Correct Answer: D

Changing a message so it can only be easily read by the intended recipient https://en.wikipedia.org/wiki/Encryption Encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor.

Correct Answer: B

Cryptoanalysis https://en.wikipedia.org/wiki/Cryptanalysis Cryptanalysis is the study of analyzing information systems in order to study the hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown.

Correct Answer: A

Asymmetric https://en.wikipedia.org/wiki/Public-key_cryptography Asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.

Correct Answer: D

Key escrow https://en.wikipedia.org/wiki/Key_escrow Key escrow (also known as a "fair" cryptosystem) is an arrangement in which the keys needed to decrypt encrypted data are held in escrow so that, under certain circumstances, an authorized third party may gain access to those keys. These third parties may include businesses, who may want access to employees' secure business-related communications, or governments, who may wish to be able to view the contents of encrypted communications (also known as exceptional access).

Correct Answer: D

The server that grants Kerberos tickets https://en.wikipedia.org/wiki/Kerberos_(protocol) The client authenticates itself to the Authentication Server (AS) which forwards the username to a key distribution center (KDC). The KDC issues a ticket-granting ticket (TGT), which is time stamped and encrypts it using the ticket-granting service's (TGS) secret key and returns the encrypted result to the user's workstation. This is done infrequently, typically at user logon; the TGT expires at some point although it may be transparently renewed by the user's session manager while they are logged in.