EC-COUNCIL 212-81 Online Practice Questions and Exam Preparation

EC-COUNCIL 212-81 Online Questions & Answers

• Question 91:

  MD5 can best be described as which one of the following?

  A. Asymmetric algorithm
  B. Hashing algorithm
  C. Digital signature
  D. Symmetric algorithm
  B. Hashing algorithm

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  Explanation

  Hashing algorithm https://en.wikipedia.org/wiki/MD5 The MD5 message-digest algorithm is a widely used hash function producing a 128-bit hash value. Although MD5 was initially designed to be used as a cryptographic hash function, it has been found to suffer from extensive vulnerabilities. It can still be used as a checksum to verify data integrity, but only against unintentional corruption. It remains suitable for other non-cryptographic purposes, for example for determining the partition for a particular key in a partitioned database.

• Question 92:

  In a ______ the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

  A. Information deduction
  B. Total break
  C. Instance deduction
  D. Global deduction
  B. Total break

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  Explanation

  Global deduction https://en.wikipedia.org/wiki/Cryptanalysis Global deduction -- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

• Question 93:

  In which of the following password protection technique, random strings of characters are added to the password before calculating their hashes?

  A. Keyed Hashing
  B. Double Hashing
  C. Salting
  D. Key Stretching
  C. Salting

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  Explanation

  Salting https://en.wikipedia.org/wiki/Salt_(cryptography) A salt is random data that is used as an additional input to a one-way function that hashes data, a password or passphrase. Salts are used to safeguard passwords in storage. Historically a password was stored in plaintext on a system, but over time additional safeguards were developed to protect a user's password against being read from the system. A new salt is randomly generated for each password. In a typical setting, the salt and the password (or its version after key stretching) are concatenated and processed with a cryptographic hash function, and the output hash value (but not the original password) is stored with the salt in a database. Hashing allows for later authentication without keeping and therefore risking exposure of the plaintext password in the event that the authentication data store is compromised. Salts defend against a pre-computed hash attack, e.g. rainbow tables.Since salts do not have to be memorized by humans they can make the size of the hash table required for a successful attack prohibitively large without placing a burden on the users. Since salts are different in each case, they also protect commonly used passwords, or those users who use the same password on several sites, by making all salted hash instances for the same password different from each other.

• Question 94:

  Which of the following statements is most true regarding binary operations and encryption?

  A. They can provide secure encryption
  B. They are only useful as a teaching method
  C. They can form a part of viable encryption methods
  D. They are completely useless
  C. They can form a part of viable encryption methods

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  Explanation

  They can form a part of viable encryption methods for example - https://en.wikipedia.org/wiki/XOR_cipher The XOR operator is extremely common as a component in more complex ciphers. By itself, using a constant repeating key, a simple XOR cipher can trivially be broken using frequency analysis. If the content of any message can be guessed or otherwise known then the key can be revealed. Its primary merit is that it is simple to implement, and that the XOR operation is computationally inexpensive. A simple repeating XOR

  (i.e. using the same key for xor operation on the whole data) cipher is therefore sometimes used for hiding information in cases where no particular security is required. The XOR cipher is often used in computer malware to make reverse engineering more difficult.

• Question 95:

  Which one of the following is a component of the PKI?

  A. CA
  B. TGS
  C. OCSP
  D. TGT
  A. CA

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  Explanation

  CA https://en.wikipedia.org/wiki/Certificate_authority 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.

• Question 96:

  How can rainbow tables be defeated?

  A. Lockout accounts under brute force password cracking attempts
  B. All uppercase character passwords
  C. Use of non-dictionary words
  D. Password salting
  D. Password salting

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  Explanation

  Password salting https://en.wikipedia.org/wiki/Salt_(cryptography)#Benefits Salts also combat the use of hash tables and rainbow tables for cracking passwords. A hash table is a large list of pre-computed hashes for commonly used passwords. For a password file without salts, an attacker can go through each entry and look up the hashed password in the hash table or rainbow table. If the look-up is considerably faster than the hash function (which it often is), this will considerably speed up cracking the file. However, if the password file is salted, then the hash table or rainbow table would have to contain "salt . password" pre-hashed. If the salt is long enough and sufficiently random, this is very unlikely. Unsalted passwords chosen by humans tend to be vulnerable to dictionary attacks since they have to be both short and meaningful enough to be memorized. Even a small dictionary (or its hashed equivalent, a hash table) is significant help cracking the most commonly used passwords. Since salts do not have to be memorized by humans they can make the size of the rainbow table required for a successful attack prohibitively large without placing a burden on the users.

• Question 97:

  Which of the following encryption algorithms relies on the inability to factor large prime numbers?

  A. RSA
  B. MQV
  C. EC
  D. AES
  A. RSA

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  Explanation

  Correct answers: RSA

  https://en.wikipedia.org/wiki/RSA_(cryptosystem)

  RSA (Rivest璖hamir瑼dleman) is a public-key cryptosystem that is widely used for secure data transmission. It is also one of the oldest. The acronym RSA comes from the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman, who

  publicly described the algorithm in 1977. An equivalent system was developed secretly, in 1973 at GCHQ (the British signals intelligence agency), by the English mathematician Clifford Cocks. That system was declassified in 1997. In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private). An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value.

  The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers.

  The security of RSA relies on the practical difficulty of factoring the product of two large prime numbers, the "factoring problem". Breaking RSA encryption is known as the RSA problem. Whether it is as difficult as the factoring problem is an

  open question. There are no published methods to defeat the system if a large enough key is used.

• Question 98:

  In IPSec, if the VPN is a gateway-gateway or a host-gateway, then which one of the following is true?

  A. IPSec does not involve gateways
  B. Only transport mode can be used
  C. Encapsulating Security Payload (ESP) authentication must be used
  D. Only the tunnel mode can be used
  D. Only the tunnel mode can be used

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  Explanation

  IPSec has two different modes: transport mode and tunnel mode.

  Only the tunnel mode can be used

  https://en.wikipedia.org/wiki/IPsec

  In tunnel mode, the entire IP packet is encrypted and authenticated. It is then encapsulated into a new IP packet with a new IP header. Tunnel mode is used to create virtual private networks for network-to-network communications (e.g.

  between routers to link sites), host- to-network communications (e.g. remote user access) and host-to-host communications (e.g. private chat).

• Question 99:

  John is going to use RSA to encrypt a message to Joan. What key should he use?

  A. A random key
  B. Joan's public key
  C. A shared key
  D. Joan's private key
  B. Joan's public key

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  Explanation

  Joan's public key https://en.wikipedia.org/wiki/RSA_(cryptosystem) Suppose Joahn uses Bob's public key to send him an encrypted message. In the message, she can claim to be Alice but Bob has no way of verifying that the message was actually from Alice since anyone can use Bob's public key to send him encrypted messages. In order to verify the origin of a message, RSA can also be used to sign a message. Suppose Alice wishes to send a signed message to Bob. She can use her own private key to do so. She produces a hash value of the message, raises it to the power of d (modulo n) (as she does when decrypting a message), and attaches it as a "signature" to the message. When Bob receives the signed message, he uses the same hash algorithm in conjunction with Alice's public key. He raises the signature to the power of e (modulo n) (as he does when encrypting a message), and compares the resulting hash value with the message's actual hash value. If the two agree, he knows that the author of the message was in possession of Alice's private key, and that the message has not been tampered with since.

• Question 100:

  A 160-bit hash algorithm developed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel for which there are 128, 256 and 320-bit versions is called what?

  A. SHA1
  B. MD5
  C. FORK
  D. RIPEMD
  D. RIPEMD

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  Explanation

  RIPEMD https://en.wikipedia.org/wiki/RIPEMD RIPEMD (RIPE Message Digest) is a family of cryptographic hash functions developed in 1992 (the original RIPEMD) and 1996 (other variants). There are five functions in the family: RIPEMD, RIPEMD-128, RIPEMD-160, RIPEMD-256, and RIPEMD-320, of which RIPEMD-160 is the most common. The original RIPEMD, as well as RIPEMD-128, is not considered secure because 128-bit result is too small and also (for the original RIPEMD) because of design weaknesses. The 256- and 320-bit versions of RIPEMD provide the same level of security as RIPEMD-128 and RIPEMD-160, respectively; they are designed for applications where the security level is sufficient but longer hash result is necessary.