In an effort to reduce data storage requirements, a company devices to hash every file and eliminate duplicates. The data processing routines are time sensitive so the hashing algorithm is fast and supported on a wide range of systems. Which of the following algorithms is BEST suited for this purpose?
A website is breached, exposing the usernames and MD5 password hashes of its entire user base. Many of these passwords are later cracked using rainbow tables. Which of the following actions could have helped prevent the use of rainbow tables on the password hashes?
A. use salting when computing MD5 hashes of the user passwords B. Use SHA as a hashing algorithm instead of MD5 C. Require SSL for all user logins to secure the password hashes in transit D. Prevent users from using a dictionary word in their password
A security analyst must ensure that the company’s web server will not negotiate weak ciphers with connecting web browsers. Which of the following supported list of ciphers MUST the security analyst disable? (Select THREE)
A. SHA B. AES C. RIPMED D. NULL E. DES F. MD5 G. TWOFISH
A security administrator implements a web server that utilizes an algorithm that requires other hashing standards to provide data integrity. Which of the following algorithms would meet the requirement?
A technician wants to verify the authenticity of the system files of a potentially compromised system. Which of the following can the technician use to verify if a system file was compromised? (Select TWO).
A. AES B. PGP C. SHA D. MD5 E. ECDHE
Correct Answer: C,D Section: Cryptography
Hashing is used to prove the integrity of data to prove that it hasn’t been modified. Hashing algorithms are used to derive a key mathematically from a message. The most common
hashing standards for cryptographic applications are the SHA and MD algorithms.
A: AES is not a hashing algorithm.
B: PGPis not a hashing algorithm.
E: ECDHE is not a hashing algorithm.
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014, pp. 255, 256
Which of the following algorithms has well documented collisions? (Select TWO).
A. AES B. MD5 C. SHA D. SHA-256 E. RSA
Correct Answer: B,C Section: Cryptography
B: MD5 biggest weakness is that it does not have strong collision resistance, and thus it is no longer recommended for use.
C: SHA-1 (also known as SHA) is being retired from most government uses; the U.S. National Institute of Standards and Technology said, “Federal agencies should stop using SHA-1
for…applications that require collision resistance as soon as practical, and must use the SHA-2 family of hash functions for these applications after 2010”, though that was later
Note: The hashing algorithm must have few or no collisions. This means that hashing two different inputs does not give the same output.
Cryptographic hash functions are usually designed to be collision resistant. But many hash functions that were once thought to be collision resistant were later broken. MD5 and SHA-1
in particular both have published techniques more efficient than brute force for finding collisions.
A: AES has much fewer hash collisions compared to both MD5 and SHA.
D: SHA-256 (also known as SHA-2) has much fewer hash collisions compared to both MD5 and SHA.
E: RSA has much fewer hash collisions compared to both MD5 and SHA.
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014, pp. 250, 252, 255, 255-256
Which of the following is used to verify data integrity?
A. SHA B. 3DES C. AES D. RSA
Correct Answer: A Section: Cryptography
SHA stands for “secure hash algorithm”. SHA-1 is the most widely used of the existing SHA hash functions, and is employed in several widely used applications and protocols
including TLS and SSL, PGP, SSH, S/MIME, and IPsec. It is used to ensure data integrity.
A hash value (or simply hash), also called a message digest, is a number generated from a string of text. The hash is substantially smaller than the text itself, and is generated by a
formula in such a way that it is extremely unlikely that some other text will produce the same hash value.
Hashes play a role in security systems where they’re used to ensure that transmitted messages have not been tampered with. The sender generates a hash of the message, encrypts
it, and sends it with the message itself. The recipient then decrypts both the message and the hash, produces another hash from the received message, and compares the two
hashes. If they’re the same, there is a very high probability that the message was transmitted intact. This is how hashing is used to ensure data integrity.
B: In cryptography, Triple DES (3DES) is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) symmetric-key block cipher, which applies the Data
Encryption Standard (DES) cipher algorithm three times to each data block. 3DES is used to encrypt data, not to verify data integrity.
C: AES (Advanced Encryption Standard) has been adopted by the U.S. government and is now used worldwide. It supersedes the Data Encryption Standard (DES) which was
published in 1977. The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data. AES is used to encrypt
data, not to verify data integrity.
D: RSA encryption is used for encrypting data in transit. RSA involves a public key and a private key. The public key can be known by everyone and is used for encrypting messages.
Messages encrypted with the public key can only be decrypted in a reasonable amount of time using the private key. RSA is used to encrypt data, not to verify data integrity.
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014, pp. 250, 251, 255-256