Cryptography and Network Security

Computing

Quiz 3 :

Classical Encryption Techniques

Quiz 3 :

Classical Encryption Techniques

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the algorithm will produce a different output depending on the specific secret key being used at the time.the exact substitutions and transformations performed by the algorithm depend on the key.
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True

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Restoring the plaintext from the ciphertext is __________ .
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A

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the process of converting from plaintext to ciphertext is known as deciphering or decryption.
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False

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__________ techniques map plaintext elements (characters, bits) into ciphertext elements.
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Steganography renders the message unintelligible to outsiders by various transformations of the text.
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An original intelligible message fed into the algorithm as input is known as _________ , while the coded message produced as output is called the __________ .
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A __________ attack involves trying every possible key until an intelligible translation of the ciphertext is obtained.
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Ciphertext generated using a computationally secure encryption scheme is impossible for an opponent to decrypt simply because the required information is not there.
True False
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A scheme known as a one-time pad is unbreakable because it produces random output that bears no statistical relationship to the plaintext.
True False
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Monoalphabetic ciphers are easy to break because they reflect the frequency data of the original alphabet.
True False
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As with Playfair, the strength of the Hill cipher is that it completely hides single letter frequencies.
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When using symmetric encryption it is very important to keep the algorithm secret.
True False
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the most widely used cipher is the Data Encryption Standard.
True False
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Joseph Mauborgne proposed an improvement to the Vernam cipher that uses a random key that is as long as the message so that the key does not need to be repeated.the key is used to encrypt and decrypt a single message and then is discarded.Each new message requires a new key of the same length as the new message.this scheme is known as a(n) __________ .
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Symmetric encryption is a form of cryptosystem in which encryption and decryption are performed using different keys.It is also known as non-conventional encryption.
True False
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Symmetric encryption remains by far the most widely used of the two types of encryption.
True False
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On average, half of all possible keys must be tried to achieve success with a brute-force attack.
True False
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With the use of symmetric encryption, the principal security problem is maintaining the secrecy of the key.
True False
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the one-time pad has unlimited utility and is useful primarily for high-bandwidth channels requiring low security.
True False
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Rotor machines are sophisticated precomputer hardware devices that use substitution techniques.
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