Cryptographic Algorithms Flashcards
Your organization wants to deploy a new encryption system that will protect the majority of data with a symmetric cipher of at least 256 bits in strength. What is the best choice of cipher for large amounts of data at rest?
RC4
3DES
AES
AES
The most likely utilized cipher is AES. It can be run at 128-, 192-, and 256-bit strengths and is considered the gold standard of current symmetric ciphers, with no known attacks, and is computationally efficient
A colleague who is performing a rewrite of a custom application that was using 3DES encryption asks you how 3DES can be more secure than the DES it is based on. What is your response?
3DES uses a key that’s three times longer.
3DES loops through the DES algorithm three times, with different keys each time.
3DES is no more secure than DES.
3DES loops through the DES algorithm three times, with different keys each time.
3DES can be more secure because it loops through the DES algorithm three times, with a different key each time: encrypt with key 1, decrypt with key 2, and then encrypt with key 3
What cipher mode is potentially vulnerable to a POODLE attack?
ECB
CBC
CTR
CBC
Cipher Block Chaining (CBC) mode is vulnerable to a POODLE (Padding Oracle On Downgraded Legacy Encryption) attack, where the system freely responds to a request about a message’s padding being correct. Manipulation of the padding is used in the attack
What cipher mode is used in the IEEE 802.1AE standard and recognized by NIST?
CTR
GCM
ECB
GCM
Galois Counter Mode (GCM) is recognized by NIST and is used in the 802.1AE standard
Your manager wants you to spearhead the effort to implement digital signatures in the organization and to report to him what is needed for proper security of those signatures. You likely have to study which algorithm?
RC4
SHA-1
RSA
RSA
Digital signatures require a public key algorithm, so most likely you need to study RSA to provide the asymmetric cryptography
Hashing is most commonly used for which of the following?
Digital signatures
Secure storage of passwords for authentication
Key management
Secure storage of passwords for authentication
Hashing is most commonly used to securely store passwords on systems so that users can authenticate to the system
A friend at work asks you to e-mail him some information about a project you have been working on, but then requests you “to hide the e-mail from the monitoring systems by encrypting it using ROT13.” What is the weakness in this strategy?
ROT13 is a very simple substitution scheme and is well understood by anyone monitoring the system, providing no security.
ROT13 is not an algorithm.
The monitoring system will not allow anything but plaintext to go through.
ROT13 is a very simple substitution scheme and is well understood by anyone monitoring the system, providing no security.
ROT13 is a simple substitution cipher that is very well known and will be simple for any person or system to decode
Why would you use PBKDF2 as part of your encryption architecture?
To use the speed of the crypto subsystems built into modern CPUs
To increase the number of rounds a symmetric cipher has to perform
To stretch passwords into secure-length keys appropriate for encryption
To stretch passwords into secure-length keys appropriate for encryption
PBKDF2 is a key stretching algorithm that stretches a password into a key of suitable length by adding a salt and then performing an HMAC to the input thousands of times
Why are hash collisions bad for malware prevention?
Malware could corrupt the hash algorithm.
Two different programs with the same hash could allow malware to be undetected.
The hashed passwords would be exposed.
Two different programs with the same hash could allow malware to be undetected.
The ability to create a program that has the same hash as a known-good program would allow malware to be undetected by detection software that uses a hash list of approved programs
What has made the PGP standard popular for so long?
Its flexible use of both symmetric and asymmetric algorithms
Simple trust model
The ability to run on any platform
Its flexible use of both symmetric and asymmetric algorithms
Pretty Good Privacy (PGP) is a popular standard because of its use of both symmetric and asymmetric algorithms when best suited to the type of encryption being done
What is a key consideration when implementing an RC4 cipher system?
Key entropy
External integrity checks
Checks for weak keys
Checks for weak keys
As RC4 is susceptible to weak keys, one key in 256 is considered weak and should not be utilized. Any implementation should have a check for weak keys as part of the protocol
Why are ephemeral keys important to key exchange protocols?
They add entropy to the algorithm.
They allow the key exchange to be completed faster.
They increase security by using a different key for each connection.
They increase security by using a different key for each connection.
Ephemeral keys are important to key exchange protocols because they ensure that each connection has its own key for the symmetric encryption, and if an attacker compromises one key, he does not have all the traffic for this connection
