212-81 Online Practice Questions and Answers

Correct Answer: B

Asymmetric Public-key cryptography, or 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

IPSec https://en.wikipedia.org/wiki/IPsec Internet Protocol Security (IPsec) is a secure network protocol suite that authenticates and encrypts the packets of data to provide secure encrypted communication between two computers over an Internet Protocol network. It is used in virtual private networks (VPNs).

Correct Answer: D

3DES https://en.wikipedia.org/wiki/Triple_DES Triple DES (3DES) has a three different keys with same size (56-bit).

Correct Answer: A

Revoked certificates https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate.It is described in RFC 6960 and is on the Internet standards track. It was created as an alternative to certificate revocation lists (CRL), specifically addressing certain problems associated with using CRLs in a public key infrastructure (PKI). Messages communicated via OCSP are encoded in ASN.1 and are usually communicated over HTTP. The "request/response" nature of these messages leads to OCSP servers being termed OCSP responders.

Correct Answer: B

plaintext https://en.wikipedia.org/wiki/Plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. Cleartext usually refers to data that is transmitted or stored unencrypted ("in clear").

Correct Answer: C

Skipjack https://en.wikipedia.org/wiki/Clipper_chip The Clipper chip was a chipset that was developed and promoted by the United States National Security Agency (NSA) as an encryption device that secured "voice and data messages" with a built-in backdoor that was intended to "allow Federal, State, and local law enforcement officials the ability to decode intercepted voice and data transmissions.". It was intended to be adopted by telecommunications companies for voice transmission. Introduced in 1993, it was entirely defunct by 1996. he Clipper chip used a data encryption algorithm called Skipjack to transmit information and the Diffie-Hellman key exchange-algorithm to distribute the cryptokeys between the peers. Skipjack was invented by the National Security Agency of the U.S. Government; this algorithm was initially classified SECRET, which prevented it from being subjected to peer review from the encryption research community. The government did state that it used an 80-bit key, that the algorithm was symmetric, and that it was similar to the DES algorithm. The Skipjack algorithm was declassified and published by the NSA on June 24, 1998. The initial cost of the chips was said to be $16 (unprogrammed) or $26 (programmed), with its logic designed by Mykotronx, and fabricated by VLSI Technology, Inc (see the VLSI logo on the image on this page).

Correct Answer: D

Diffusion https://en.wikipedia.org/wiki/Confusion_and_diffusion Diffusion means that if we change a single bit of the plaintext, then (statistically) half of the bits in the ciphertext should change, and similarly, if we change one bit of the ciphertext, then approximately one half of the plaintext bits should change.[2] Since a bit can have only two states, when they are all re-evaluated and changed from one seemingly random position to another, half of the bits will have changed state. The idea of diffusion is to hide the relationship between the ciphertext and the plain text. This will make it hard for an attacker who tries to find out the plain text and it increases the redundancy of plain text by spreading it across the rows and columns; it is achieved through transposition of algorithm and it is used by block ciphers only.

Correct Answer: C

Steganography https://en.wikipedia.org/wiki/Steganography Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video. The word steganography comes from Greek steganographia, which combines the words steganos , meaning "covered or concealed", and -graphia meaning "writing".

Correct Answer: A

Type 1 https://en.wikipedia.org/wiki/NSA_cryptography#Type_1_Product A Type 1 Product refers to an NSA endorsed classified or controlled cryptographic item for classified or sensitive U.S. government information, including cryptographic equipment, assembly or component classified or certified by NSA for encrypting and decrypting classified and sensitive national security information when appropriately keyed.

Correct Answer: C

Any number only divisible by one and itself https://en.wikipedia.org/wiki/Prime_number A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 ?5 or 5 ?1, involve 5 itself. However, 4 is composite because it is a product (2 ?2) in which both numbers are smaller than 4. Primes are central in number theory because of the fundamental theorem of arithmetic: every natural number greater than 1 is either a prime itself or can be factorized as a product of primes that is unique up to their order.