Digital signature


A digital code (generated and authenticated by public key encryption ) which is attached

To an electronically transmitted document to verify its contents and the sender's identify.  

A digital signature is a most mathematical scheme for demonstrating the authenticity of a digital message or documents .

A valid digital signature gives a recipient reason to believe that the message was created by a known sender and that the message was not altered in transit

Digital signatures are a standard  element of most cryptographic protocolare commonly used for software distribution

Applications of digital signatures:

Digital signatures can provide added assurances of the evidence to provenance, identity and status of an electronic document as well as acknowledging informed consent and approval by a signatory.

The United States govt. printing office (GPO) publishers electronic version of the budget.

Some Reasons for applying a Digital signature to communication.

  • Authentication
  • Integrity
  • Non-repudiation
For additional security there are some precautions:

1. Putting a private key on smart card: All public key/private key cryptosystem depend entirely on keeping the private secret .A private   key can be stored on a user's computer and protected by a local password but this has two disadvantages

The user can omly sign documents on that particular computer.

The security of the private key depended entirely on the security of the computer.

2. Using smart card readers with a separate keyboard: Enter in a pin code to activate the smart card commonly requires a numeric keypad.

3. Other smart card design: Smart card design is active field ,and there are smart card schemes which are intended to avoid these particular problems ,though so far with little security profs.

4. Using digital signature only with trusted applications: One of the main difference b/w a digital signature is that the user does not "see" what he signs.

Python Programming ↓ 👆
Java Programming ↓ 👆
JAVA covered following topics in these notes.
JAVA Programs
Principles of Programming Languages ↓ 👆
Principles of Programming Languages covered following topics in these notes.

Previous years solved papers:
A list of Video lectures References:
  1. Sebesta,”Concept of programming Language”, Pearson Edu 
  2. Louden, “Programming Languages: Principles & Practices” , Cengage Learning 
  3. Tucker, “Programming Languages: Principles and paradigms “, Tata McGraw –Hill. 
  4. E Horowitz, "Programming Languages", 2nd Edition, Addison Wesley

    Computer Organization and Architecture ↓ 👆

    Computer Organization and Architecture covered following topics in these notes.

    1. Structure of desktop computers
    2. Logic gates
    3. Register organization
    4. Bus structure
    5. Addressing modes
    6. Register transfer language
    7. Direct mapping numericals
    8. Register in Assembly Language Programming
    9. Arrays in Assembly Language Programming


    1. William stalling ,“Computer Architecture and Organization” PHI
    2. Morris Mano , “Computer System Organization ”PHI

    Computer Network ↓ 👆
    Computer Network covered following topics in these notes.
    1. Data Link Layer
    2. Framing
    3. Byte count framing method
    4. Flag bytes with byte stuffing framing method
    5. Flag bits with bit stuffing framing method
    6. Physical layer coding violations framing method
    7. Error control in data link layer
    8. Stop and Wait scheme
    9. Sliding Window Protocol
    10. One bit sliding window protocol
    11. A protocol Using Go-Back-N
    12. Selective repeat protocol
    13. Application layer
    1. Andrew S. Tanenbaum, David J. Wetherall, “Computer Networks” Pearson Education.
    2. Douglas E Comer, “Internetworking with TCP/IP Principles, Protocols, And Architecture",Pearson Education
    3. KavehPahlavan, Prashant Krishnamurthy, “Networking Fundamentals”, Wiley Publication.
    4. Ying-Dar Lin, Ren-Hung Hwang, Fred Baker, “Computer Networks: An Open Source Approach”, McGraw Hill.