Question 21 : In transposition, the plaintext letters are
1. Substituted
2. Rearranged
3. Removed
4. None of the mentioned
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Question 22 : PGP offers _____ block ciphers for message encryption.
1. Triple-DES
2. CAST
3. IDEA
4. All of the mentioned
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Question 23 : For n input bits the number of substitution patterns are
1. 2n
2. (2n)!
3. 1/2n!
4. 2n!
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Question 24 : These three ciphers can operate of ______ of plaintext and cipher text.
1. 128 bit blocks
2. 64 bit blocks
3. 256 bit blocks
4. 156 bit blocks
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Question 25 : In cipher feedback method, encryption is done on
1. Single individual bits
2. Characters
3. Single individual bits & Characters
4. None of the mentioned
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Question 26 : The substitution of the letters are done
1. Serially
2. Parallel way
3. Serially & Parallel way
4. None of the mentioned
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Question 27 : Which block cipher has key length of 128 bits?
1. IDEA
2. CAST
3. IDEA & CAST
4. None of the mentioned
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Question 28 : A cryptographic hash function has variable output length.
1. True
2. False
3.
4.
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Question 29 : For digital signatures private key cryptosystem is used.
1. True
2. False
3.
4.
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Question 30 : In public key cryptosystem which is kept as public?
1. Encryption keys
2. Decryption keys
3. Encryption & Decryption keys
4. None of the mentioned
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