3i Infotech Papers: Sample Questions 564 - 565 of 1245

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Question number: 564

» Database » Oracle

MCQ▾

Question

What are the different events in Triggers?

Choices

Choice (4) Response

a.

Drop, Comment

b.

Insert, Update, Delete

c.

Define, Create

d.

Question does not provide sufficient data or is vague

Answer

b.

Explanation

  • Trigger event specifies what DML statement can initiate the trigger- INSERT, DELETE, or UPDATE operation on the table or view, or a SELECT operation that queries the table.

  • Create trigger statement must specify one trigger event.

  • We can define triggers that are activated by INSERT, DELETE, UPDATE, or SELECT statements.

  • Multiple triggers on the same table or view can active different type of trigger by the same type of trigger event.

  • We cannot specify a DELETE event if the triggering table has a referential constraint that specifies ON DELETE CASCADE.

  • Guaranty is that triggering statement returns the same result with and without the trigger action on a table.

  • Statement from an external database server can activate the trigger.

  • The INSTEAD OF trigger replaces the trigger event with the specified trigger action.

  • Any number INSTEAD OF trigger can be defined for each type of INSERT, DELETE, or UPDATE triggering event.

Question number: 565

» Basic CS » Networks

Essay Question▾

Describe in Detail

What is wide-mouth frog?

Explanation

  • The simplest known key distribution centre authentication protocol.

  • A key distribution centre is part of a cryptosystem intended to reduce risks in exchanging keys.

  • Allows individuals communicating over a network to prove identity to each other preventing reply attack.

  • Provides detection of modification.

  • Prevention of unauthorized reading.

  • First described under the name “The Wide-mouthed-frog Protocol” in the paper “A Logic of Authentication”.

  • The protocol can be specified as follows in security protocol notation.

  • Security protocol notation:

  • The protocol has several problems:

  • Requires a global clock.

  • The server has access to all keys- single point of failure and attack

  • The value of the shared key between “A” and “B” is completely determined by “A”- an attacker can pretend to be “A”

  • Can replay messages within period when timestamp is valid.

  • “A” is not assured that “B” exists.

  • Protocol is stateful.