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Free 212-81 Exam Braindumps (page: 4)

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PDF with 206 Questions

What advantage do symmetric algorithms have over asymmetric algorithms

  1. It is easier to implement them in software
  2. They are more secure
  3. They are faster
    D It is easier to exchange keys

Answer(s): C

Explanation:

They are faster Symmetric key encryption is much faster than asymmetric key encryption, because both the sender and the recipient of a message to use the same secret key.



Which one of the following is an example of a symmetric key algorithm?

  1. ECC
  2. Diffie-Hellman
  3. RSA
  4. Rijndael

Answer(s): D

Explanation:

Rijndael https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
The Advanced Encryption Standard (AES), also known by its original name Rijndael. The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data.

Incorrect answers:
ECC - Elliptic-curve cryptography is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fields) to provide equivalent security.
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.
RSA - Rivest–Shamir–Adleman 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.



The greatest weakness with symmetric algorithms is ____________.

  1. They are less secure than asymmetric
  2. The problem of key exchange
  3. The problem of generating keys
  4. They are slower than asymmetric

Answer(s): B

Explanation:

The problem of key exchange https://en.wikipedia.org/wiki/Symmetric-key_algorithm
Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext. The keys may be identical or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. This requirement that both parties have access to the secret key is one of the main drawbacks of symmetric key encryption, in comparison to public-key encryption (also known as asymmetric key encryption).



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

  1. IPSec does not involve gateways
  2. Only transport mode can be used
  3. Encapsulating Security Payload (ESP) authentication must be used
  4. Only the tunnel mode can be used

Answer(s): D

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).

Incorrect answers:
Encapsulating Security Payload (ESP) authentication must be used. ESP in transport mode does not provide integrity and authentication for the entire IP packet. However, in Tunnel Mode, where the entire original IP packet is encapsulated with a new packet header added, ESP protection is afforded to the whole inner IP packet (including the inner header) while the outer header (including any outer IPv4 options or IPv6 extension headers) remains unprotected.
IPSec does not involve gateways. Wrong.
Only transport mode can be used. Transport mode, the default mode for IPSec, provides for end-to- end security. It can secure communications between a client and a server. When using the transport mode, only the IP payload is encrypted.






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