Eccouncil 212-81 Practice Exam Questions & Answers

Explanation

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 Vigenre cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846.

Incorrect answers:

Integral Cryptanalysis - uses lots of sets of plaintext that are similar with slight modifications. These are encrypted and then the variations are analyzed to determine if there's anything that can be zeroed in on.

Information Deduction - the attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known.

Birthday Attack - cryptographic attack that exploits the mathematics behind the birthday problem in the probability theory forces collisions within hashing functions.

Explanation ECB mode is the simplest symmetric encryption mode because it treats the message as independent blocks and encrypts each one identically using the same key. This straightforward approach makes it easy to understand and implement. However, this simplicity is also its weakness. Because identical plaintext blocks produce identical ciphertext blocks, patterns in the original message leak through to the encrypted output. This vulnerability is why ECB is generally not recommended for real-world use despite being theoretically sound for individual block encryption.

Explanation

Kerberos

https://en.wikipedia.org/wiki/Kerberos_(protocol)

Kerberos is a computer-network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. The protocol was named after the character Kerberos (or Cerberus) from Greek mythology, the ferocious three-headed guard dog of Hades. Its designers aimed it primarily at a client--server model and it provides mutual authentication---both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks.

Kerberos builds on symmetric key cryptography and requires a trusted third party, and optionally may use public-key cryptography during certain phases of authentication. Kerberos uses UDP port 88 by default.

Incorrect answers:

ElGamal - ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie--Hellman key exchange. It was described by Taher Elgamal in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature scheme, which should not be confused with ElGamal encryption.

Diffie-Hellman - 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 conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman.[1][2] DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography. Published in 1976 by Diffie and Hellman, this is the earliest publicly known work that proposed the idea of a private key and a corresponding public key.

Yarrow - algorithm is a family of cryptographic pseudorandom number generators (CPRNG) devised by John Kelsey, Bruce Schneier, and Niels Ferguson and published in 1999. The Yarrow algorithm is explicitly unpatented, royalty-free, and open source; no license is required to use it. Yarrow is incorporated in iOS and macOS for their /dev/random devices, and was in FreeBSD (where it is superseded by Fortuna).

Explanation

Key Schedule

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

In cryptography, the so-called product ciphers are a certain kind of cipher, where the (de-)ciphering of data is typically done as an iteration of rounds. The setup for each round is generally the same, except for round-specific fixed values called a round constant, and round-specific data derived from the cipher key called a round key. A key schedule is an algorithm that calculates all the round keys from the key.

Incorrect answers:

Feistel Network - (also known as Luby--Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel who did pioneering research while working for IBM (USA).

SHA-2 - (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the Merkle--Damgrd structure, from a one-way compression function itself built using the Davies--Meyer structure from a specialized block cipher.

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 conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman.

Explanation

SHA-1

https://en.wikipedia.org/wiki/SHA-1

SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest -- typically rendered as a hexadecimal number, 40 digits long. It was designed by the United States National Security Agency, and is a U.S. Federal Information Processing Standard.

SHA-1 produces a message digest based on principles similar to those used by Ronald L. Rivest of MIT in the design of the MD2, MD4 and MD5 message digest algorithms, but generates a larger hash value (160 bits vs. 128 bits).

Explanation

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 stegans , meaning 'covered or concealed', and -graphia meaning 'writing'.