212-81 Practice Exam Questions and Answers

If the round function is a cryptographically secure pseudorandom function, then ___rounds is sufficient to make it a "strong" pseudorandom permutation.

Part of understanding cryptography is understanding the cryptographic primitives that go into any crypto system. A(n) _______ is a fixed-size input to a cryptographic primitive that is random or pseudorandom.

Which of the following algorithms uses three different keys to encrypt the plain text?

You are studying classic ciphers. You have been examining the difference between single substitution and multi-substitution. Which one of the following is an example of a multi-alphabet cipher?

The art and science of writing hidden messages so that no one suspects the existence of the message, a type of security through obscurity. Message can be hidden in picture or audio file for example. Uses least significant bits in a file to store data.

Which of the following statements is most true regarding binary operations and encryption?

You are explaining the details of the AES algorithm to cryptography students. You are discussing the derivation of the round keys from the shared symmetric key. The portion of AES where round keys are derived from the cipher key using Rijndael's key schedule is called what?

A measure of the uncertainty associated with a random variable.

A number that is used only one time, then discarded is called what?

Frank is trying to break into an encrypted file… He is attempting all the possible keys that could be used for this algorithm. Attempting to crack encryption by simply trying as many randomly generated keys as possible is referred to as what?

What is the largest key size that AES can use?

What type of encryption uses different keys to encrypt and decrypt the message?

Which of the following Secure Hashing Algorithm (SHA) produces a 160-bit digest from a message with a maximum length of (264-1) bits and resembles the MD5 algorithm?

What is Kerchoff's principle?

A non-secret binary vector used as the initializing input algorithm for encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance.

With Cipher feedback (CFB) what happens?

Which of the following is an asymmetric algorithm related to the equation y^2 = x^3 + Ax + B?

Which component of IPsec performs protocol-level functions that are required to encrypt and decrypt the packets?

Which one of the following is an authentication method that sends the username and password in cleartext?

The mode makes a block cipher into a synchronous stream cipher. It generates keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext.

What is a "Collision attack" in cryptography?

Which one of the following terms describes two numbers that have no common factors?

Nicholas is working at a bank in Germany. He is looking at German standards for pseudo random number generators. He wants a good PRNG for generating symmetric keys. The German Federal Office for Information Security (BSI) has established four criteria for quality of random number generators. Which ones can be used for cryptography?

Which one of the following attempts to hide data in plain view?

Which of the following is a substitution cipher used by ancient Hebrew scholars?

Algorithm that was chosen for the Data Encryption Standard, which was altered and renamed Data Encryption Algorithm.

Basic information theory is the basis for modern symmetric ciphers. Understanding the terminology of information theory is, therefore, important. Changes to one character in the plaintext affect multiple characters in the ciphertext. What is this referred to?

Storing private keys with a third party is referred to as what?

A cryptographic hash function which 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 MD6-256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.

In order to understand RS

A.  

Which one of the following is an algorithm that uses variable length key from 1 to 256 bytes, which constitutes a state table that is used for subsequent generation of pseudorandom bytes and then a pseudorandom string of bits, which is XORed with the plaintext to produce the ciphertext?

As a network administrator, you have implemented WPA2 encryption in your corporate wireless network. The WPA2's ________ integrity check mechanism provides security against a replay attack.

A transposition cipher invented 1918 by Fritz Nebel, used a 36 letter alphabet and a modified Polybius square with a single columnar transposition.

If you use substitution alone, what weakness is present in the resulting cipher text?

Protocol suite provides a method of setting up a secure channel for protected data exchange between two devices.

Original, unencrypted information is referred to as ____.

This is a proprietary version of PAP. Encrypts username and password as it is sent across network.

Which of the following is the successor of SSL?

A cipher is defined as what

Which analysis type is based on the statistics of the numbers of unique colors and close-color pairs in a 24-bit image, a method that analyzes the pairs of colors created by LSB embedding?

A _______ 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

Which of the following acts as a verifier for the certificate authority?

A protocol for key aggreement based on Diffie-Hellman. Created in 1995. Incorporated into the public key standard IEEE P1363.

A simple algorithm that will take the initial key and from that generate a slightly different key each round.

What does Output feedback (OFB) do:

When learning algorithms, such as RSA, it is important to understand the mathematics being used. In RSA, the number of positive integers less than or equal to some number is critical in key generation. The number of positive integers less than or equal to n that are coprime to n is called ______.

If Bob is using asymmetric cryptography and wants to send a message to Alice so that only she can decrypt it, what key should he use to encrypt the message?

Collision resistance is an important property for any hashing algorithm. Joan wants to find a cryptographic hash that has strong collision resistance. Which one of the following is the most collisionresistant?

Which one of the following best describes a process that splits the block of plaintext into two separate blocks, then applies the round function to one half, and finally swaps the two halves?

The Clipper chip is notable in the history of cryptography for many reasons. First, it was designed for civilian used secure phones. Secondly, it was designed to use a very specific symmetric cipher. Which one of the following was originally designed to provide built-in cryptography for the Clipper chip?

What advantage do symmetric algorithms have over asymmetric algorithms

Asymmetric encryption method developed in 1984. It is used in PGP implementations and GNU Privacy Guard Software. Consists of 3 parts: key generator, encryption algorithm, and decryption algorithm.

Which of the following is assured by the use of a hash?

In a ______ the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

Which one of the following is an example of a symmetric key algorithm?

Network of trusted certificate authority servers. Use asymmetric key pairs and combines software, encryption and services to provide a means of protecting security of business communication and transactions.

In a Feistel cipher, the two halves of the block are swapped in each round. What does this provide?

What is the formula m^e %n related to?

How does Kerberos generate the first secret key in the authentication process?

Developed by Netscape and has been replaced by TLS. It was the preferred method used with secure websites.

Bob’s password is hashed, and so is John’s. Even though they used different passwords, the hash is the same. What is this called?