212-81 Online Practice Questions and Answers

Correct Answer: B

https://en.wikipedia.org/wiki/Advanced_Encryption_Standard Rijndael is a family of ciphers with different key and block sizes. For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.

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

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: D

MD6 https://en.wikipedia.org/wiki/MD6 The MD6 Message-Digest Algorithm is a cryptographic hash function. It uses a Merkle tree- like structure to allow for immense parallel computation of hashes for very long inputs. Authors claim a performance of 28 cycles per byte for MD6256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.[2] The source code of the reference implementation was released under MIT license. Speeds in excess of 1 GB/s have been reported to be possible for long messages on 16- core CPU architecture. In December 2008, Douglas Held of Fortify Software discovered a buffer overflow in the original MD6 hash algorithm's reference implementation. This error was later made public by Ron Rivest on 19 February 2009, with a release of a corrected reference implementation in advance of the Fortify Report.

Correct Answer: D

WPA2

https://en.wikipedia.org/wiki/Wi-Fi_Protected_Access#WPA2 WPA2 use the Counter Mode-Cipher Block Chaining (CBC)-Message Authentication Code (MAC) Protocol (CCMP).

Correct Answer: D

Diffie-Hellman https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange Diffie-Hellman key exchange is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as originally conceptualized by Ralph Merkle and named after Whitfield Diffie and Martin Hellman. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography.

Correct Answer: A

Avalanche https://en.wikipedia.org/wiki/Avalanche_effect In cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.

Correct Answer: B

Asymmetric https://en.wikipedia.org/wiki/Public-key_cryptography 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: A

The algorithm(s) needed to encrypt and decrypt a message https://en.wikipedia.org/wiki/Cipher In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption--a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography.

Correct Answer: A

https://en.wikipedia.org/wiki/Advanced_Encryption_Standard For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.