Digital Signatures

Digital Signature helps to prohibit the access of the intruders in a network system, as the sender sends the message to a signature and the receiver only receives the message with valid signatures .

Summary

Digital Signature helps to prohibit the access of the intruders in a network system, as the sender sends the message to a signature and the receiver only receives the message with valid signatures .

Things to Remember

  • the sender needs to have the digital signature
  • only authorized signatures are accepted

MCQs

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Subjective Questions

Q1:

Write short notes on the digestive system.


Type: Short Difficulty: Easy

Show/Hide Answer
Answer: <h4>Digestive system</h4>
<ul>
<li><strong>Digestion</strong> <br />The process of breaking down food by mechanical and enzymatic action in the alimentary canal into substances that can be used by the body. The process in the alimentary canal by which food is broken up physically, as by the action of the teeth, and chemically, as by the action of enzymes, and converted into a substance suitable for absorption and assimilation into the body.<br />&bull;<strong> Digestive system</strong><br />Every cell in the body requires food for heat and energy and growth and repair of tissues. For that reason, we need to eat food and to digest it. So the group of organs works for ingestion, digestion, absorption and excretion of food is collectively called digestive system.<br /><br />As food passes through the digestive tract, it is broken by physical and chemical means until it is in a form suitable for absorption into the blood stream and utilization within the body. There are certain constituents of the diet, which cannot be digested and absorbed therefore they are excreted in the form of feces. The continuing process or serial act of mechanism comes under the system of digestive.</li>
</ul>
<h4>Structure and function of digestive organs involved in digestive system</h4>
<p><br />A. The Alimentary or Gastro &ndash; intestinal tract<br />B. The Accessory glands or organs</p>
<p><strong>A. The Alimentary Tract</strong></p>
<p>It is a long tube of about 8-10 meters, starts at the mouth and terminates at the anus through which food passes, absorbs and excretes. <br />There are various parts:</p>
<p>a) Mouth :<br />i. Tongue <br />ii. Teeth<br /><br />b) Pharynx<br /><br />c) Esophagus<br /><br />d) Stomach <br /><br />e) Small intestine:<br />i. Duodenum<br />ii. Jejunum<br />iii. Ileum <br /><br />f) Large intestine:<br />i. Caecum<br />ii. Ascending colon<br />iii. Transverse colon<br />iv. Descending colon<br />v. Pelvic or sigmoid colon<br />vi. Rectum<br /><br />g) Anal canal</p>
<p><strong>B. The accessory organs</strong><br />Accessory organs are those organs, which partially help in the digestive system. Such an accessory organs have various secretion, which is poured in the alimentary tract either by glands in the lining membrane of the organs or by glands situated outside the tract i.e. duct (pancreatic juice, bile etc). The accessory glands are:<br /><br />a) Three pairs of salivary glands<br />b) Pancreas<br />c) Liver<br />d) Gallbladder<br />e) Bile ducts<br />A. The alimentary tract<br />a) Mouth</p>
<p>&nbsp;</p>
<h4>&nbsp;</h4>

Videos

Digestive System
Digital Signatures

Digital Signatures

Digital Signature

A cryptographic technique is analogous to hand-written signatures. Message with no signature or with unauthorized signature is not accepted by the system. In Network system, a sender (Bob) digitally signs documents, establishing his documents owner/creator.

Verifiable: recipient (Alice) can prove to someone that Bob, and no one else (including Alice), must have signed the document.

Fig: Creating a digital signature for a document
Fig: Creating a digital signature for a document

  • Suppose Alice receives message m, digital signature K-B(m)
  • Alice verifies m signed by Bob by applying Bob’s public key K+B(m) to K-B(m) then checks K+B(K-B(m)) = m.
  • If K+B(K-B(m)) = m, whoever signed m must have used Bob’s private key.

  • Alice thus verifies that:

  1. Bob signed m. (Authentication)
  2. No one else signed m.
  3. Bob signed m and not m’. (Message Integrity)

  • Non-repudiation:

  1. Alice can take m, and signature KB(m) to court and prove that Bob signed m.

References:

  1. A.S. Tanenbaum, “Computer Networks”, 3rd Edition, Prentice Hall India, 1997.
  2. W. Stallings, “Data and Computer Communication”, Macmillan Press, 1989.
  3. Kurose Ross, “Computer Networking: A top-down approach”, 2nd Edition, Pearson Education
  4. Larry L. Peterson, Bruce S. Davie, “Computer Networks: A Systems Approach”, 3rd Edition, Morgan Kaufmann Publishers

Lesson

Network Security

Subject

Computer Engineering

Grade

Engineering

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