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NEW QUESTION 85
Modern symmetric ciphers all make use of one or more s-boxes. Both Feistel and non-Feistel ciphers use these s-boxes. What is an s-box?
- A. A black box for the algorithm implementation
- B. A shifting box where input bits are shifted
- C. A substitution box where input bits are replaced
- D. Another name for the round function
Answer: C
Explanation:
Substitution box where input bits are replaced
https://en.wikipedia.org/wiki/S-box
In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext - Shannon's property of confusion.
NEW QUESTION 86
Which one of the following wireless standards uses the Advanced Encryption Standard (AES) using the Counter Mode-Cipher Block Chaining (CBC)-Message Authentication Code (MAC) Protocol (CCMP)?
- A. WEP2
- B. WPA2
- C. WEP
- D. WPA
Answer: B
Explanation:
WPA2
https://en.wikipedia.org/wiki/Wi-Fi_Protected_Access#WPA2
WPA2 use the Counter Mode-Cipher Block Chaining (CBC)-Message Authentication Code (MAC) Protocol (CCMP).
NEW QUESTION 87
What is Kerchoff's principle?
- A. Only the key needs to be secret, not the actual algorithm
- B. A minimum of 15 rounds is needed for a Feistel cipher to be secure
- C. A minimum key size of 256 bits is necessary for security
- D. Both algorithm and key should be kept secret
Answer: A
Explanation:
Only the key needs to be secret, not the actual algorithm
https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle
Kerckhoffs's principle of cryptography was stated by Netherlands born cryptographer Auguste Kerckhoffs in the 19th century: A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.
NEW QUESTION 88
This is a proprietary version of PAP. Encrypts username and password as it is sent across network.
- A. Kerberos
- B. WPA2
- C. S-PAP
- D. PPTP VPN
Answer: C
Explanation:
S-PAP
Shiva Password Authentication Protocol (S-PAP) - PAP with encryption for the usernames/passwords that are transmitted.
Incorrect answers:
Kerberos - a computer-network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. Its designers aimed it primarily at a client-server model and it provides mutual authentication-both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks.
WPA2 - (Wi-Fi Protected Access II) security certification program developed by the Wi-Fi Alliance to secure wireless computer networks. It includes mandatory support for CCMP, an AES-based encryption mode.
PPTP VPN - works at layer 2 (data link) layer of OSI model. Provides both authentication and encryption. EAP or CHAP is used to provide the authentication for PPTP. MPPE (Microsoft Point to Point Encryption) is used to encrypt the traffic. MPPE - a specific Microsoft implementation of DES. Can only use over a traditional Ethernet network.
NEW QUESTION 89
Which of the following is the standard for digital certificates?
- A. 509 is a standard defining the format of public key certificates. X.509 certificates are used in many Internet protocols, including TLS/SSL, which is the basis for HTTPS, the secure protocol for browsing the web. They are also used in offline applications, like electronic signatures. An X.509 certificate contains a public key and an identity (a hostname, or an organization, or an individual), and is either signed by a certificate authority or self-signed. When a certificate is signed by a trusted certificate authority, or validated by other means, someone holding that certificate can rely on the public key it contains to establish secure communications with another party, or validate documents digitally signed by the corresponding private key.
- B. 509
https://en.wikipedia.org/wiki/X.509 - C. CA
- D. X.509
- E. CRL
- F. RFC 2298
Answer: D
NEW QUESTION 90
If you wished to see a list of revoked certificates from a CA, where would you look?
- A. CA
- B. CRL
- C. RFC
- D. RA
Answer: B
Explanation:
CRL
https://ru.wikipedia.org/wiki/Certificate_Revocation_List
Certificate Revocation List (or CRL) is "a list of digital certificates that have been revoked by the issuing certificate authority (CA) before their scheduled expiration date and should no longer be trusted".
Incorrect answers:
RA - Used to proxy the certificate requests on behalf of the user and validate whether or not they are legitimate instead of having the user go directly to the CA. The RA talks to the subordinate CA on behalf of the user, which makes it harder for the actor to get directly to the certificate authority and do harm.
RFC - Request for Comments (RFC) is a publication from the Internet Society (ISOC) and its associated bodies, most prominently the Internet Engineering Task Force (IETF), the principal technical development and standards-setting bodies for the Internet.
CA - certificate authority or certification authority is an entity that issues digital certificates
NEW QUESTION 91
What does the OCSP protocol provide?
- A. VPN connectivity
- B. Encryption
- C. Hashing
- D. Revoked certificates
Answer: D
Explanation:
Revoked certificates
https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol
The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate.It is described in RFC 6960 and is on the Internet standards track. It was created as an alternative to certificate revocation lists (CRL), specifically addressing certain problems associated with using CRLs in a public key infrastructure (PKI). Messages communicated via OCSP are encoded in ASN.1 and are usually communicated over HTTP. The "request/response" nature of these messages leads to OCSP servers being termed OCSP responders.
NEW QUESTION 92
Which one of the following uses three different keys, all of the same size?
- A. RSA
- B. DES
- C. AES
- D. 3DES
Answer: D
Explanation:
3DES
https://en.wikipedia.org/wiki/Triple_DES
Triple DES (3DES or TDES), officially the Triple Data Encryption Algorithm (TDEA or Triple DEA), is a symmetric-key block cipher, which applies the DES cipher algorithm three times to each data block.
NEW QUESTION 93
Which algorithm was U. S. Patent 5,231,668, filed on july 26, 1991, attributed to David W. Kravitz, and adopted by the U. S. government in 1993 with FIPS 186?
- A. RC4
- B. RSA
- C. DSA
- D. AES
Answer: C
Explanation:
DSA
https://en.wikipedia.org/wiki/Digital_Signature_Algorithm
DSA is covered by U.S. Patent 5,231,668 , filed July 26, 1991 and now expired, and attributed to David
W. Kravitz, a former NSA employee. This patent was given to "The United States of America as represented by the Secretary of Commerce, Washington, D.C.", and NIST has made this patent available worldwide royalty-free. Claus
P. Schnorr claims that his U.S. Patent 4,995,082 (also now expired) covered DSA; this claim is disputed.
NEW QUESTION 94
What is the basis for the FISH algorithm?
- A. The Lagged Fibonacci generator
- B. Equations that describe an ellipse
- C. The difficulty in factoring numbers
- D. Prime number theory
Answer: A
Explanation:
The Lagged Fibonacci generator
https://en.wikipedia.org/wiki/FISH_(cipher)
The FISH (FIbonacci SHrinking) stream cipher is a fast software based stream cipher using Lagged Fibonacci generators, plus a concept from the shrinking generator cipher. It was published by Siemens in 1993. FISH is quite fast in software and has a huge key length. However, in the same paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few thousand bits of known plaintext.
NEW QUESTION 95
Widely used, particularly with Microsoft operating systems. Created by MIT and derives its name from the mythical three headed dog. The is a great deal of verification for the tickets and the tickets expire quickly. Client authenticates to the Authentication Server once using a long term shared secret and receives back a Ticket-Granting Server. Client can reuse this ticket to get additional tickets without reusing the shared secret. These tickets are used to prove authentication to the Service Server.
- A. Kerberos
- B. ElGamal
- C. Diffie-Hellman
- D. Yarrow
Answer: A
Explanation:
Kerberos
https://en.wikipedia.org/wiki/Kerberos_(protocol)
Kerberos is a computer-network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. The protocol was named after the character Kerberos (or Cerberus) from Greek mythology, the ferocious three-headed guard dog of Hades. Its designers aimed it primarily at a client-server model and it provides mutual authentication-both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks.
Kerberos builds on symmetric key cryptography and requires a trusted third party, and optionally may use public-key cryptography during certain phases of authentication. Kerberos uses UDP port 88 by default.
Incorrect answers:
ElGamal - ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie-Hellman key exchange. It was described by Taher Elgamal in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature scheme, which should not be confused with ElGamal encryption.
Diffie-Hellman - Diffie-Hellman key exchange is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman.[1][2] DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography. Published in 1976 by Diffie and Hellman, this is the earliest publicly known work that proposed the idea of a private key and a corresponding public key.
Yarrow - algorithm is a family of cryptographic pseudorandom number generators (CPRNG) devised by John Kelsey, Bruce Schneier, and Niels Ferguson and published in 1999. The Yarrow algorithm is explicitly unpatented, royalty-free, and open source; no license is required to use it. Yarrow is incorporated in iOS and macOS for their /dev/random devices, and was in FreeBSD (where it is superseded by Fortuna).
NEW QUESTION 96
_____ uses at least two different shifts, changing the shift with different letters in the plain text.
- A. Caesar cipher
- B. Atbash
- C. Scytale
- D. multi-alphabet encryption
Answer: D
Explanation:
multi-alphabet encryption
https://en.wikipedia.org/wiki/Polyalphabetic_cipher
Two different shifts create two different alphabets.
For +1 and +2
Plaintext alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
2 ciphertext alphabets
B C D E F G H I J K L M N O P Q R S T U V W X Y Z A
C D E F G H I J K L M N O P Q R S T U V W X Y Z A B
Incorrect answers:
Scytale - transposition cipher
Caesar cipher - monoalphabetic cipher
Atbash - monoalphabetic cipher
NEW QUESTION 97
In a Feistel cipher, the two halves of the block are swapped in each round. What does this provide?
- A. Diffusion
- B. Confusion
- C. Avalanche
- D. Substitution
Answer: B
Explanation:
Confusion
https://en.wikipedia.org/wiki/Confusion_and_diffusion#Definition
Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two.
The property of confusion hides the relationship between the ciphertext and the key.
This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of the values of most or all of the bits in the ciphertext will be affected.
Confusion increases the ambiguity of ciphertext and it is used by both block and stream ciphers.
Incorrect answer:
Avalanche - The avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.
Diffusion - Diffusion means that if we change a single bit of the plaintext, then (statistically) half of the bits in the ciphertext should change, and similarly, if we change one bit of the ciphertext, then approximately one half of the plaintext bits should change.[2] Since a bit can have only two states, when they are all re-evaluated and changed from one seemingly random position to another, half of the bits will have changed state.
Substitution - Substitution technique is a classical encryption technique where the characters present in the original message are replaced by the other characters or numbers or by symbols.
NEW QUESTION 98
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?
- A. Transposition
- B. A mistake
- C. Convergence
- D. A collision
Answer: D
Explanation:
A collision
https://en.wikipedia.org/wiki/Collision_(computer_science)
A collision or clash is a situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.
NEW QUESTION 99
If the round function is a cryptographically secure pseudorandom function, then ___rounds is sufficient to make it a "strong" pseudorandom permutation.
- A. 0
- B. 1
- C. 2
- D. 3
Answer: A
Explanation:
4
https://en.wikipedia.org/wiki/Feistel_cipher
Michael Luby and Charles Rackoff analyzed the Feistel cipher construction, and proved that if the round function is a cryptographically secure pseudorandom function, with Ki used as the seed, then 3 rounds are sufficient to make the block cipher a pseudorandom permutation, while 4 rounds are sufficient to make it a "strong" pseudorandom permutation (which means that it remains pseudorandom even to an adversary who gets oracle access to its inverse permutation). Because of this very important result of Luby and Rackoff, Feistel ciphers are sometimes called Luby-Rackoff block ciphers.
NEW QUESTION 100
Which service in a PKI will vouch for the identity of an individual or company?
- A. CR
- B. KDC
- C. CA
- D. CBC
Answer: C
Explanation:
CA
https://en.wikipedia.org/wiki/Certificate_authority
A certificate authority or certification authority (CA) is an entity that issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. This allows others (relying parties) to rely upon signatures or on assertions made about the private key that corresponds to the certified public key. A CA acts as a trusted third party-trusted both by the subject (owner) of the certificate and by the party relying upon the certificate. The format of these certificates is specified by the X.509 or EMV standard.
NEW QUESTION 101
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