WGU Course C839 - Intro to Cryptography Quizlet by Brian MacFarlane

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

A Symmetric

B Private key

C Secure

D Asymmetric

D

The most widely used asymmetric encryption algorithm is what?

A RSA

B Vigenere

C DES

D Caesar Cipher

A

Original, unencrypted information is referred to as ____.

A text

B plaintext

C cleantext

D ciphertext

B

Which of the following is NOT an asymmetric system?

A PGP

B RSA

C SSL

D DES

D

In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys?

A User A's public key

B User A's private key

C User B's public key

D User B's private key

C

The greatest weakness with symmetric algorithms is _____.

A They are less secure than asymmetric

B The problem of key exchange

C They are slower than asymmetric

D The problem of generating keys

B

Which of the following is generally true about block sizes?

A Smaller block sizes increase security

B Block sizes must be more than 256 bits to be secure

C Block size is irrelevant to security

D Larger block sizes increase security

D

A _____ is a function that takes a variable-size input m and returns a fixed-size string.

A Symmetric cipher

B Hash

C Asymmetric cipher

D Feistel

B

Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel?

A Elliptic Curve

B RSA

C MD5

D Diffie-Hellman

D

A _________ is a digital representation of information that identifies you as a relevant entity by a trusted third party?

A Digital Signature

B Hash

C Ownership stamp

D Digest

A

What is the standard used by most digital certificates?

A X.509

B CRL

C RFC 2298

D OCSP

A

DES uses keys of what size?

A 56 bits

B 192 bits

C 128 bits

D 64 bits

A

Which of the following is NOT a key size used by AES?

A 512 bits

B 128 bits

C 192 bits

D 256 bits

A

Which of the following was a multi alphabet cipher widely used from the 16th century (1553) to the early 20th century (1900s)?

A Vigenere

B Caesar

C Atbash

D Scytale

A

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

A Caesar

B Vigenere

C Scytale

D Atbash

D

Shifting each letter in the alphabet a fixed number of spaces to the right or left is an example of what?

A Bit shifting

B Confusion

C Multi substitution

D Single substitution

D

Which of the following most accurately defines encryption?

A changing a message so it can only be easily read by the intended recipient

B Making binary changes to a message to conceal it

C changing a message using complex mathematics

D Applying keys to plain text

A

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

A It is the same length as the original text

B It is easily broken with modern computers.

C It is too simple.

D Because it maintains letter and word frequency.

D

_____ uses at least two different shifts, changing the shift with different letters in the plain text.

A Atbash

B multi-alphabet encryption

C Scytale

D Caesar cipher

B

____ was designed to provide built in cryptography for the clipper chip.

A Blowfish

B Skipjack

C GOST

D 3DES

B

Which of the following uses an 80 bit key on 64 bit blocks?

A Twofish

B AES

C Skipjack

D DES

C

With _____, the message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption.

A Electronic codebook (ECB)

B Cipher-block chaining (CBC)

C Cipher feedback (CFB)

D Output feedback (OFB)

A

Which of the following is an example of an unbalanced Feistel?

A 3DES

B Skipjack

C Twofish

D AES

B

This process is done by having each block of plaintext is XORed with the previous ciphertext block before being encrypted.

A Output feedback (OFB)

B Cipher-block chaining (CBC)

C Electronic codebook (ECB)

D Cipher feedback (CFB)

B

The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block is called what?

A Output feedback (OFB)

B Cipher-block chaining (CBC)

C Cipher feedback (CFB)

D Electronic codebook (ECB)

C

This is a method for turning a block cipher into a stream cipher by generating a keystream block, which are then XORed with the plaintext blocks to get the ciphertext.

A Cipher feedback (CFB)

B Electronic codebook (ECB)

C Output feedback (OFB)

D Cipher-block chaining (CBC)

C

Which of the following modes can be used to turn a block cipher into a stream cipher?

A Propagating cipher-block chaining (PCBC) and Electronic codebook (ECB)

B Counter Mode (CTR) and Propagating cipher-block chaining (PCBC)

C Electronic codebook (ECB) and Output feedback (OFB)

D Output feedback (OFB) and Counter Mode (CTR)

D

A fixed-size pseudorandom number that is fed into a symmetric cipher to increase randomness is called what?

A IV

B Key

C Chain

D Salt

A

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

A Nonce

B Chain

C Salt

D IV

A

Which of the following is a stream cipher that uses variable length key from 1 to 256 bytes?

A RC4

B AES

C DESx

D DES

A

This algorithm was published by the German engineering firm Seimans in 1993. It is a software based stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers.

A RC4

B Blowfish

C FISH

D Twofish

C

Which of the following is NOT required for a hash?

A Minimum key length of 256 bits

B Variable-length input, fixed-length output

C Non-reversible

D Few collisions

A

A ______ refers to a situation where two different inputs yield the same output.

A Substitution

B Convergence

C Collision

D Transposition

C

What is a salt?

A Key rotation

B Random bits intermixed with a hash to increase randomness and reduce collisions.

C Random bits intermixed with a symmetric cipher to increase randomness and make it more secure.

D Key whitening

B

RFC 1321 describes what hash?

A RIPEMD

B SHA1

C GOST

D MD5

D

What size block does FORK256 use?

A 256

B 128

C 512

D 64

C

In 1977 researchers at MIT described what asymmetric algorithm?

A RSA

B AES

C DH

D EC

A

What is the formula (M^e)(%n) related to?

A Encrypting with EC

B Generating Mersenne primes

C Decrypting with RSA

D Encrypting with RSA

C

Which of the following equations is related to EC?

A P = Cd%n

B Me%n

C y2 = x3 + Ax + B

D Let m = (p-1)(q-1)

C

U.S. Patent 5,231,668 and FIPS 186 define what algorithm?

A AES

B RSA

C Elliptic Curve (EC)

D Digital Signature Algorithm (DSA)

D

What is X.509?

A The standard for PGP certificates

B The standard for encrypting email

C The standard for FIPS 186

D The standard for digital certificates

D

What is contained in a CRL?

A Keys for RSA

B New certificates

C Revoked certificates

D Keys for AES

C

What does the Online Certificate Status Protocol (OCSP) provide?

A Revoked certificates

B Hashing

C VPN connectivity

D Encryption

A

In terms of cryptanalysis, what does it mean to break a cipher?

A finding a method to decrypt a message that is at least twice as efficient as brute force

B trying every possible key until you can decrypt the message

C deploying an algorithm that uses a 228 bit key

D finding any method to decrypt the message that is more efficient than brute force

D

An authentication method that periodically re-authenticates the client by establishing a hash that is then resent from the client is called ______.

A PAP

B CHAP

C SPAP

D EAP

B

What is a TGS?

A The server that grants Kerberos tickets

B protocol for encryption

C protocol for key exchange

D The server that escrows keys

A

What is Kerchoff's principle?

A A minimum key size of 256 bits is necessary for security.

B Both algorithm and key should be kept secret.

C A minimum of 15 rounds is needed for a Feistel cipher to be secure.

D Only the key needs to be secret, not the actual algorithm.

D

Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publically disclosed without damaging security?

A Babbage's principle

B Kerkchoff's principle

C Vigenere's principle

D Shamir's principle

B

A process that puts a message into the least significant bits of a binary file is called what?

A Symmetric cryptography

B Masking

C Steganography

D Asymmetric cryptography

C

If you wished to see a list of revoked certificates from a CA, where would you look?

A CRL

B CA

C RFC

D RA

A

Which of the following is generally true about block ciphers?

A Secret block ciphers should be trusted.

B Block ciphers permute the bits of the input plaintext.

C The plaintext and ciphertext are always the same size.

D A block cipher is an encryption function for variable-size blocks of data.

C

What does the OCSP protocol provide?

A encryption

B VPN connectivity

C hashing

D a real time protocol for verifying certificates

D

U.S. encryption standard that replaced DES. Block symmetric cipher that uses 128-bit block sizes and various key lengths (128, 192, 256).

AES

DES, 3DES, SHA, AES (some AES implementations are Type I)

Class 3 Algorithms

Encryption method where the sender and receiver use an instance of the same key for encryption and decryption purposes.

Symmetric

Block symmetric algorithm chosen by NIST as an encryption standard in 1976. It uses a 56-bit true key bit size, 64-bit block size, and 16 rounds of computation.

Data Encryption Standard (DES)

technical specification indicating how multimedia data and e-mail binary attachments are to be transferred.

Multipurpose Internet Mail Extensions (MIME)

Valid data transmission is maliciously or fraudulently repeated to allow an entity gain unauthorized access.

Replay Attack

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

Internet Protocol Security (IPSec)

Juniper (block cipher)

MAYFLY (asymmetric)

FASTHASH (hashing)

WALBURN (high bandwith link encryption)

PEGASUS (satellite telemetry)

Class 1 Algorithms

Component of a PKI that creates and maintains digital certificates throughout their life cycles.

Certificate Authority

Uses public key encryption and provides data encryption, server authentication, message integrity, and optional client authentication.

It is currently at version 3.0.

Secure Sockets Layer (SSL)

Manipulating individuals so that they will divulge confidential information, rather than by breaking in or using technical cracking techniques.

Social engineering attack

Cryptanalysis attack where the attacker is assumed to have access only to a set of ciphertexts.

Ciphertext-only attack

servers and software signing, for which independent verification and checking of identity and authority is done by issuing CA

Class 3 Certificates

it should be impossible for any attacker to calculate, or otherwise guess, from any given subsequence, any previous or future values in the sequence

BSI Criteria K3 states

Cryptanalysis attack that uses identified statistical patterns.

Statistical attack

organizations for which proof of identity is required

Class 2 Certificates

Block symmetric cipher that uses a 128-bit key and 64-bit block size.

International Data Encryption Algorithm (IDEA)

individuals, and intended for email

Class 1 Certificates

A form of cryptanalysis applicable to symmetric key algorithms that was invented by Eli Biham and Adi Shamir.

The examination of differences in an input and how that affects the resultant difference in the output.

Differential cryptanalysis

Cryptanalysis attack where the attacker is assumed to have access to sets of corresponding plaintext and ciphertext.

Known plaintext attack

Carries out real-time validation of a certificate and reports back to the user whether the certificate is valid, invalid, or unknown.

OCSP checks the CRL that is maintained by the CA.

Online Certificate Status Protocol (OCSP)

What is the formula Me%n related to?

Encrypting with RSA

Plain-text is equal to the encryption function (E) with the key (k) and the ciphertext (c) being passed as parameters to that function

P= E(k,c) Symmetric decryption

Not certified for government use

Class 4 algorithms

64 bit algorithm operating at 56 bits with an 8 bit parity block

DES

AH is the authenticating protocol, and ESP is an authenticating and encrypting protocol that uses cryptographic mechanisms to provide source authentication, confidentiality, and message integrity.

Authentication Header (AH) and Encapsulating Security Payload (ESP).

developed as a Russian national standard and produced fixed length outputs of 256 bits

GOST

A measure of the uncertainty associated with a random variable

Entropy

Attempts to make the statistical frequencies of the ciphertext and actual key as complex as possible

Confusion

Like AES, Serpent has a block size of 128 bits and can have a key size of 128, 192, or 256 bits. The algorithm is also a substitution-permutation network like AES. It uses 32 rounds working with a block of four 32-bit words. Each round applies one of eight 4-bit to 4-bit S-boxes 32 times in parallel. Designed by Ross Anderson, Eli Biham, and Lars Knudsen.

Serpent

What is the difference between Secure HTTP (SHTTP) and HTTP Secure (HTTPS)?

S-HTTP is a technology that protects each message sent between two computers, while HTTPS protects the communication channel between two computers, messages and all.

Which of the following was a multi alphabet cipher widely used from the 16th century to the early 20th century?

Vigenere

A _____ is a function that takes a variable-size input m and returns a fixed-size string.

Hash

A small change that yields large effects in the output.

Avalanche

Private organizations or governmental security

Class 5 Certificates

Numbers that have no factors in common with another.

Co-prime numbers

Cryptanalysis attack that exploits vulnerabilities within the intrinsic algebraic structure of mathematical functions.

Algebraic attack

Designed by Ross Anderson and Eli Biham in 1995. The size of a ________ hash value is 192 bits.

TIGER

In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys?

User B's public key

Public key algorithm that can be used for digital signatures, encryption, and key exchange.

an extension of the Diffie-Hellman algorithm.

El Gamal

Block symmetric cipher that was chosen to fulfill the Advanced Encryption Standard. It uses a 128-bit block size and various key lengths (128, 192, 256).

Rijndael

Published by Siemens in 1993. A software-based stream cipher

using a Lagged Fibonacci generator (pseudorandom number generator).

FISH

128 bit hash. RFC 1321

MD5

Cipher text (C) is equal to the encryption function (E) with the key (k) and plain-text (p) being passed as parameters to that function

C = E(k,p) Symmetric encryption

It is impossible to compress the data such that the code is less than the Shannon entropy of the source, without it being virtually certain that information will be lost

Shannon's source coding theorem

A non-secret binary vector used as the initializing input algorithm for

the encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance.

IV (Initialization Vector)

If a cryptanalysis uncovers a method that can derive a key for an algorithm, but is only slightly faster than brute force, what is this called?

Success

• Confidentiality

• Access control

• Integrity

• Authentication

• Nonrepudiation

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