Cryptography Flashcards
CISSP Cryptography Domain
- What is the goal of cryptanalysis?
a. To determine the strength of an algorithm
b. To increase the substitution functions in a cryptographic algorithm
c. To decrease the transposition functions in a cryptographic algorithm
d. To determine the permutations used
- The answer is A. Cryptanalysis is the process of trying to reverse-engineer a cryptosystem with the goal of uncovering the key that was used. Once this key is uncovered all other messages encrypted with this key can be accessed. Cryptanalysis is carried out by the white hats to test the strength of the algorithm.
- The brute force attacks have increased because ___________.
a. The increased use of permutations and transpositions in algorithms.
b. As algorithms get stronger, they get less complex, and thus more susceptible to attacks.
c. The increase in processor speed and power.
d. The reduction in key length over time.
- The answer is C. A brute-force attack is very resource intensive. It is guessing different values over and over again until the correct one is obtained. As computers have more powerful processors added to them attackers can carry out more powerful brute-force attacks.
- Which of the following is not a property or characteristic of a one-way hash function?
a. It converts a message of arbitrary length into a value of fixed length.
b. Given the digest value, it should be computationally infeasible to find the corresponding message.
c. It should be computationally infeasible to derive the same digest from two different messages.
d. It converts a message of fixed length to an arbitrary length value
- The answer is D. A hashing algorithm will take a string of variable length, the
message can be of any size, and compute a fixed length value. The fixed length value
is the message digest. The MD family creates the fixed length value of 128 bits and
SHA creates one of 160 bits.
- What would indicate that a message had been modified?
a. The public key has been altered.
b. The private key has been altered.
c. The message digest has been altered.
d. The message has been encrypted properly.
- The answer is C. Hashing algorithms generate message digests to detect if
modification has taken place. The sender and receiver independently generate their
own digests and the receiver compares these values. If they are different, the receiver
knows the message had been alter in some way.
- Which of the following is an algorithm used in a U.S. Standard for creating secure message digests?
a. Data Encryption Standard
b. Digital Signature Standard
c. Secure Hash Algorithm
d. Data Signature Standard
- The answer is C. SHA was created to generate secure message digests. Digital Signature Standard (DSS) is the standard to create digital signatures, which dictates that SHA must be used. DSS also outlines the following digital signature algorithms can be used with SHA; RSA, DSA, ECDSA.
- If an attacker stole a password file that contained one-way encrypted passwords, what type of attack would she perform to find the encrypted passwords?
a. Man-in-the-middle attack (transmission)
b. Birthday attack
c. Denial of service attack (Attack on Availability)
d. Dictionary attack
- The answer is D. A dictionary attack is carried out by comparing a captured password against a list of commonly used words. The list is usually fed into a dictionary attacking tool.
- What is an advantage of RSA over the DSA?
a. It can provide digital signature and encryption functionality.
b. It uses fewer resources and encrypts quicker because it uses symmetric keys.
c. It is a block cipher versus a stream cipher.
d. It employs a one-time encryption pad. (IPSec or SSL)
- The answer is A. RSA can be used for data encryption, key exchange, and digital signatures. DSA can only be used for digital signatures.
- Many countries restrict the use or exportation of cryptographic systems. What is the reason given when these types of restrictions are put into place?
a. Without standards, there would be many interoperability issues when trying to employ different algorithms into different programs.
b. It can be used by some countries against their local people.
c. Criminals could use encryption to avoid detection and prosecution.
d. Laws are way behind, so adding different types of encryption would confuse the laws more.
- The answer is C. The U.S. has greatly reduced their restrictions on cryptography exportation, but there are still some restrictions in place. Products that use encryption cannot be sold to any country the U.S. has declared as terrorist. The fear is that the enemies of the country will use encryption to hide their communication and the government would not be able to properly break this encryption and spy on their data transfers.
- What is used to create a digital signature?
a. The receiver’s private key
b. The sender’s public key
c. The sender’s private key
d. The receiver’s public key
- The answer is C. A digital signature is a message digest that has been encrypted with the sender’s private key. A sender, or anyone else, should never have access to the receiver’s private key.
- Which of the following best describes a digital signature?
a. A method of transferring a handwritten signature to an electronic document
b. A method to encrypt confidential information (Confidentiality Algorithms anyone?)
c. A method to provide an electronic signature and encryption
d. A method to let the receiver of the message prove the source and integrity of a message
- The answer is D. A digital signature provides authentication (knowing who really sent the message), integrity (because a hashing algorithm is involved), and non-repudiation (sender cannot deny sending the message).
- How many bits make up the effective DES key?
a. 56
b. 64
c. 32
d. 16
- The answer is A. DES has a key size of 64-bits, but 8 bits are used for parity, so the true key size is 56 bits. Remember that DEA is the algorithm used for the DES standard so DEA has a true key size of 56 bits also because we are actually talking about the same algorithm here. DES is really the standard and DEA is the algorithm, we just call it DES in the industry because it is easier.
- When would a certificate authority revoke a certificate?
a. If the user’s public key has become compromised
b. If the user changed over to using the PEM model that uses a web of trust
c. If the user’s private key has become compromised
d. If the user moved to a new location
- The answer is C. The reason that a certificate is revoked is to warn others who use that person’s public key that they should no longer trust the public key. For some reason that public key is no longer bound to that particular individual’s identity. This could be because an employee left the company, a person changed their name and needed a new certificate, but most likely it is because the person’s private key was compromised.
- What does DES stand for?
a. Data Encryption System
b. Data Encryption Standard
c. Data Encoding Standard
d. Data Encryption Signature
- The answer is B. Data Encryption Standard was developed by NIST and NSA to be used to encrypt sensitive but unclassified government data.
- Which of the following best describes a certificate authority?
a. An organization that issues private keys and the corresponding algorithms
b. An organization that validates encryption processes
c. An organization that verifies encryption keys
d. An organization that issues certificates
- The answer is D. A registration authority (RA) will accept a person’s request for a certificate and verify that person’s identity. Then the RA sends this request to a certificate authority (CA), which generates and maintains the certificate. There are companies in business solely for this purpose; Entrust and VeriSign are just two examples.
- What does the acronym DEA stand for?
a. Data Encoding Standard
b. Data Encoding Application
c. Data Encryption Algorithm
d. Digital Encryption Algorithm
- The answer is C. DEA is the algorithm that fulfilled the DES standard. So DEA has all of the attributes of DES; block symmetric cipher that uses 64-bit blocks, 16 rounds, and a 56-bit key.
