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The Acronym DES stands for
Answer: Digital Encryption Standard
Answer: permutation and substitution on 64 bit blocks of plain text
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(i) is a symmetric key encryption method
(ii) guarantees absolute security
(iii) is implementable as hardware VLSI chip
(iv) is a public key encryption method
Answer: i and iii
Answer: Can be broken with presently available high performance computers.
Answer: Working on 64-bit blocks of plain text and 56 bit keys by applying DES algorithm for three rounds.
Answer: Cannot be broken in reasonable time using presently available computers.
Answer: in which each person who wants to communicate has two keys; a private key known to him only and a public key which is publicized to enable others to send message to him.
Answer: there is no key distribution problem as public key can be kept in a commonly accessible database.
Answer: A encrypts message using B’s public key
Answer: the authority checks and assures customers that the public key indeed belongs to the business which claims its ownership
Answer: public keys of subscribers
Answer: sends message key using public key encryption using DES and hashed message using public key encryption
(i) must give a hashed message which is shorter than the original message
(ii)must be hardware implementable
(iii) two different messages should not give the same hashed message
(iv) is not essential for implementing digital signature
Answer: i and iii
(i) to tie an electronic message to the sender’s identity
(ii)for non repudiation of communication by a sender
(iii) to prove that a message was sent by the sender in a court of law
(iv) in all e-mail transactions
Answer: i, ii, iii
Answer: an authentication of an electronic record by tying it uniquely to a key only a sender knows
(i) to speed up encrypted message transmission
(ii) to ensure higher security by using different key for each transmission
(iii) as a combination is always better than individual system
(iv) as it is required in e-Commerce
Answer: i and ii
Answer: encrypting plain text by a different random key for each message transmission and sending the key to the receiver using a public key system
Answer: if B knows it is from A he can decrypt it using A’s public key
