Eccouncil 212-81 Certified Encryption Specialist ECES Exam Practice Test

Answer : B

Null Ciphers

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

A null cipher, also known as concealment cipher, is an ancient form of encryption where the plaintext is mixed with a large amount of non-cipher material. Today it is regarded as a simple form of steganography, which can be used to hide ciphertext.

Incorrect answers:

Caesar Cipher - Monoalphabetic cipher where letters are shifted one or more letters in either direction. The method is named after Julius Caesar, who used it in his private correspondence.

Vigenre - method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution.

Playfair Cipher - manual symmetric encryption technique and was the first literal digram substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of Lord Playfair for promoting its use.

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.

Incorrect answers:

Type 2 - product refers to an NSA endorsed unclassified cryptographic equipment, assemblies or components for sensitive but unclassified U.S. government information.

Type 3 - unclassified cryptographic equipment, assembly, or component used, when appropriately keyed, for encrypting or decrypting unclassified sensitive U.S. Government or commercial information, and to protect systems requiring protection mechanisms consistent with standard commercial practices. A Type 3 Algorithm refers to NIST endorsed algorithms, registered and FIPS published, for sensitive but unclassified U.S. government and commercial information.

Type 4 - Algorithm refers to algorithms that are registered by the NIST but are not FIPS published. Unevaluated commercial cryptographic equipment, assemblies, or components that are neither NSA nor NIST certified for any Government usage.

Answer : A

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 first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. Generally, the hidden messages appear to be (or to be part of) something else: images, articles, shopping lists, or some other cover text. For example, the hidden message may be in invisible ink between the visible lines of a private letter. Some implementations of steganography that lack a shared secret are forms of security through obscurity, and key-dependent steganographic schemes adhere to Kerckhoffs's principle.

Incorrect answers:

Avalanche effect - 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.

Cryptosystem - a suite of cryptographic algorithms needed to implement a particular security service, most commonly for achieving confidentiality (encryption)

Key Schedule - an algorithm for the key that calculates the subkeys for each round that the encryption goes through.

Answer : D

Single substitution

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

Substitution of single letters separately---simple substitution---can be demonstrated by writing out the alphabet in some order to represent the substitution. This is termed a substitution alphabet. The cipher alphabet may be shifted or reversed (creating the Caesar and Atbash ciphers, respectively) or scrambled in a more complex fashion, in which case it is called a mixed alphabet or deranged alphabet.

Answer : A

Chosen Plaintext Attack

https://en.wikipedia.org/wiki/Chosen-plaintext_attack

A chosen-plaintext attack (CPA) is an attack model for cryptanalysis which presumes that the attacker can obtain the ciphertexts for arbitrary plaintexts. The goal of the attack is to gain information that reduces the security of the encryption scheme.

Incorrect answers:

Rainbow Tables - precomputed table for caching the output of cryptographic hash functions, usually for cracking password hashes.

Transposition - swapping blocks of text.

Steganography - the practice of concealing a file, message, image, or video within another file, message, image, or video.

Answer : C

Correct answers: Co-prime numbers

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

Two integers a and b are said to be relatively prime, mutually prime, or coprime if the only positive integer (factor) that evenly divides both of them is 1. Consequently, any prime number that divides one of a or b does not divide the other. This is equivalent to their greatest common divisor (gcd) being 1.

The numerator and denominator of a reduced fraction are coprime. The numbers 14 and 25 are coprime, since 1 is their only common divisor. On the other hand, 14 and 21 are not coprime, because they are both divisible by 7.

Incorrect answers:

Even Numbers - A formal definition of an even number is that it is an integer of the form n = 2k, where k is an integer; it can then be shown that an odd number is an integer of the form n = 2k + 1 (or alternately, 2k - 1). It is important to realize that the above definition of parity applies only to integer numbers, hence it cannot be applied to numbers like 1/2 or 4.201. See the section 'Higher mathematics' below for some extensions of the notion of parity to a larger class of 'numbers' or in other more general settings.

Fibonacci Numbers - commonly denoted F_n, form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1.

Mersenne Primes - is a prime number that is one less than a power of two. That is, it is a prime number of the form M_n = 2^n 1 for some integer n. They are named after Marin Mersenne, a French Minim friar, who studied them in the early 17th century. If n is a composite number then so is 2^n 1. Therefore, an equivalent definition of the Mersenne primes is that they are the prime numbers of the form M_p = 2^p 1 for some prime p.

Answer : D

Password salting

https://en.wikipedia.org/wiki/Salt_(cryptography)#Benefits

Salts also combat the use of hash tables and rainbow tables for cracking passwords. A hash table is a large list of pre-computed hashes for commonly used passwords. For a password file without salts, an attacker can go through each entry and look up the hashed password in the hash table or rainbow table. If the look-up is considerably faster than the hash function (which it often is), this will considerably speed up cracking the file. However, if the password file is salted, then the hash table or rainbow table would have to contain 'salt . password' pre-hashed. If the salt is long enough and sufficiently random, this is very unlikely. Unsalted passwords chosen by humans tend to be vulnerable to dictionary attacks since they have to be both short and meaningful enough to be memorized. Even a small dictionary (or its hashed equivalent, a hash table) is significant help cracking the most commonly used passwords. Since salts do not have to be memorized by humans they can make the size of the rainbow table required for a successful attack prohibitively large without placing a burden on the users.