Q. Which are the most frequently found letters in the English language ?

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Q. Choose from among the following cipher systems, from best to the worst, with respect to ease of decryption using frequency analysis.

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Q. On Encrypting “thepepsiisintherefrigerator” using Vignere Cipher System using the keyword “HUMOR” we get cipher text-

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Q. On Encrypting “cryptography” using Vignere Cipher System using the keyword “LUCKY” we get cipher text

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Q. The Index of Coincidence for English language is approximately

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Q. If all letters have the same chance of being chosen, the IC is approximately

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Q. Consider the cipher text message with relative frequencies:

4 0 10 25 5 32 24 15 6 11 5 5 1 2 6 6 15 19 10 0 6 28 8 2 3 2
The Index of Coincidence is

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Q. Consider the cipher text message:

YJIHX RVHKK KSKHK IQQEV IFLRK QUZVA EVFYZ RVFBX UKGBP KYVVB QTAJK TGBQO ISGHU CWIKX QUXIH DUGIU LMWKG CHXJV WEKIH HEHGR EXXSF DMIIL UPSLW UPSLW AJKTR WTOWP IVXBW NPTGW EKBYU SBQWS

Relative Frequencies –
3 7 2 2 5 5 7 9 11 4 14 4 2 1 3 4 6 5 6 5 7 10 9 8 4 2

The Index of Coincidence is –

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Q. A symmetric cipher system has an IC of 0.041. What is the length of the key ‘m’?

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Q. In public key cryptosystem _____ keys are used for encryption and decryption.

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Q. In public key cryptosystem which is kept as public?

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Q. In a trapdoor function, the functions are easy to go in

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Q. Pretty good privacy program is used for

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Q. PGP system uses

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Q. Private key algorithm is used for _____ encryption and public key algorithm is used for _____ encryption.

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Q. Which are called the block ciphers?

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Q. Which has a key length of 128 bits?

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Q. Which algorithm can be used to sign a message?

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Q. Examples of hash functions are

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Q. A cryptographic hash function has variable output length.

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