An encryption scheme is unconditionally secure if the ciphertext generated does not contain enough information to determine uniquely the corresponding plaintext, no matter how much cipher text is available

CRYPTOGRAPHY AND NETWORK SECURITY - ENCRYPTION TECHNIQUES MCQ

• In brute force attack, on average half of all possible keys must be tried to achieve success
• If the sender and receiver use different keys, the system is referred to as conventional cipher system
• Divide (HAPPY)26 by (SAD)26. We get quotient –
• Dividing (11001001) by (100111) gives remainder –
• pi in terms of base 26 is
• The time required to convert a k-bit integer to its representation in the base 10 in terms of big-O notation is
• In base 26, multiplication of YES by NO gives –
• Division of (131B6C3) base 16 by (lA2F) base 16 yeilds –
• An encryption scheme is unconditionally secure if the ciphertext generated does not contain enough information to determine uniquely the corresponding plaintext, no matter how much cipher text is available
• The estimated computations required to crack a password of 6 characters from the 26 letter alphabet is-
• Use Caesar’s Cipher to decipher the following: HQFUBSWHG WHAW
• Caesar Cipher is an example of
• Monoalphabetic ciphers are stronger than Polyalphabetic ciphers because frequency analysis is tougher on the former
• Which are the most frequently found letters in the English language ?
• Choose from among the following cipher systems, from best to the worst, with respect to ease of decryption using frequency analysis
• On Encrypting “thepepsiisintherefrigerator” using Vignere Cipher System using the keyword “HUMOR” we get cipher text-
• On Encrypting “cryptography” using Vignere Cipher System using the keyword “LUCKY” we get cipher text
• The Index of Coincidence for English language is approximately
• If all letters have the same chance of being chosen, the IC is approximately
• Consider the cipher text message with relative frequencies:
• Consider the cipher text message:
• A symmetric cipher system has an IC of 0.041. What is the length of the key ‘m’?
• In public key cryptosystem _____ keys are used for encryption and decryption
• In public key cryptosystem which is kept as public?
• In a trapdoor function, the functions are easy to go in
• Pretty good privacy program is used for
• PGP system uses
• Private key algorithm is used for _____ encryption and public key algorithm is used for _____ encryption
• Which are called the block ciphers?
• Which has a key length of 128 bits?
• Which algorithm can be used to sign a message?
• Examples of hash functions are
• A cryptographic hash function has variable output length
• A set of numbers is called as super increasing if
• Knapsack problem can be solved by
• Merkle hellman is a symmetric cryptosystem
• In Merkle Hellman method same key is used for encryption and decryption
• Cipher system can be solved effectively by statistically using
• Encryption transformations are known as
• For n input bits the number of substitution patterns are
• In transposition, the plaintext letters are
• The substitution of the letters are done
• In cipher feedback method, encryption is done on
• In stream encryption, the key sequence repeats itself
• In which method, key-stream is generated independently?
• Synchronous ciphers uses
• Public key cryptosystem uses same key for both encryption and decryption
• Which should be kept as a secret in public key cryptosystem?
• Public key cryptosystem is also known as
• Euler’s totient function is determined by
• Pretty good privacy (PGP) security system uses
• Public key cryptosystem is used for the encryption of
• For digital signatures private key cryptosystem is used
• Data compression includes
• PGP offers _____ block ciphers for message encryption
• Which block cipher has key length of 128 bits?
• These three ciphers can operate of ______ of plaintext and cipher text
• The key size of DES is
• Which operation is used in encryption using IDEA?
• What is the key size allowed in PGP?
• Which algorithm is used for public key encryption?
• Which should be used first to decrypt?
• The digital signature provides authentication to the
• In hash function output length is fixed
• The hash function
• DSA protocol is based on

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