1 of 14

ELECTRONICS AND COMMUNICATION

BY�SHIVANGI SINGH

CYBER SECURITY (2150002)��“DIGITAL SIGNATURE”

2 of 14

INTRODUCTION

  • The authenticity of many legal, financial, and other documents is done by the presence or absence of an authorized handwritten signature.
  • “Digital Signature” is the best solution for authenticity in various fields.
  • A digital signature is nothing but an attachment to any piece of electronic information, which represents the content of the document and the identity of the owner of that document uniquely.

​

​

3 of 14

WHAT IS DIGITAL SIGNATURE

  • Hash value of a message when encrypted with the private key of a person is his digital signature on that e-Document.
  • Digital Signature of a person therefore varies from document to document thus ensuring authenticity of each word of that document.
  • As the public key of the signer is known, anybody can verify the message and the digital signature.

​

4 of 14

WHY DIGITAL SIGNATURES???

  • To provide Authenticity, Integrity and Non-repudiation to electronic documents.
  • To use the Internet as the safe and secure medium for e-Commerce and e-Governance.

​

5 of 14

BASIC REQUIREMENTS….

  • Private Key

The private key is one which is accessible only to the signer. It is used to generate the digital signature which is then attached to the message.

  • Public Key

The public key is made available to all those who receive the signed messages from the sender. It is used for verification of the received message.

​

6 of 14

BASIC REQUIREMENTS…

  • Digital Signature Certificate
  • A subscriber of the private key and public key pair makes the public key available to all those who are intended to receive the signed messages from the subscriber.
  • But in case of any dispute between the two sides, there must be some entity with the receiver which will allow the receiver of the message to prove that the message was sent by the subscriber of the key pair. This can be done with the Digital Signature Certificate.

​

7 of 14

HOW THE TECHNOLOGY WORKS??

The digital signature can be considered as a numerical value that is represented as a sequence of characters. The creation of a digital signature is a complex mathematical process that can only be created by a computer.

  • Consider a scenario where A has to digitally sign a file or an email and send it to B.
  • ‘A’ selects the file to be digitally signed or clicks on 'sign' in email application
  • The hash value of the file content or the message is calculated by A's computer
  • This hash value is encrypted with A's Signing Key (which is a Private Key) to create the Digital Signature.

8 of 14

…...

  • After B receives the signed message, the associated application (such as email application) identifies that the message has been signed. B's computer then proceeds to:
    • Decrypt the Digital Signature using A's Public Key
    • Calculate the hash of the original message
    • Compare the (a) hash it has computed from the received message with the (b) decrypted hash received with A's message.
  • Any difference in the hash values would reveal tampering of the message.

​

9 of 14

…...

10 of 14

DIGITAL SIGNATURE ALGORITHMS

11 of 14

DIGITAL SIGNATURE ALGORITHMS

  • RSA-based signature schemes, such as RSA-PSS
  • DSA and its elliptic curve variant ECDSA
  • Edwards-curve Digital Signature Algorithm and its Ed25519 variant.
  • ElGamal signature scheme as the predecessor to DSA, and variants Schnorr signature and Pointcheval–Stern signature algorithm
  • Rabin signature algorithm
  • Pairing-based schemes such as BLS
  • NTRUSign is an example of a digital signature scheme based on hard lattice problems
  • Undeniable signatures
  • Aggregate signature - a signature scheme that supports aggregation: Given n signatures on n messages from n users, it is possible to aggregate all these signatures into a single signature whose size is constant in the number of users. This single signature will convince the verifier that the n users did indeed sign the n original messages. A scheme by Mihir Bellare and Gregory Neven may be used with Bitcoin.
  • Signatures with efficient protocols - are signature schemes that facilitate efficient cryptographic protocols such as zero-knowledge proofs or secure computation

12 of 14

DIGITAL SIGNATURES

  • I agree

Efcc61c1c03db8d8ea8569545c073c814a0ed755

  • My place of birth is at Gwalior.

fe1188eecd44ee23e13c4b6655edc8cd5cdb6f25

  • I am 62 years old.

0e6d7d56c4520756f59235b6ae981cdb5f9820a0

  • I am an Engineer.

ea0ae29b3b2c20fc018aaca45c3746a057b893e7

  • I am a Engineer.

01f1d8abd9c2e6130870842055d97d315dff1ea3

These are digital signatures of same person on different documents

​

13 of 14

APPLICATIONS …..

  • Electronic Mail
  • Data storage
  • Electronic funds transfer
  • Software Distribution
  • Smart Card
  • ISDN
  • Time Stamped Signature
  • Blind Signatures

​

14 of 14

DRAWBACKS

  • The private key must be kept in a secured manner.
  • The process of generation and verification of digital signature requires considerable amount of time.
  • For using the digital signature the user has to obtain private and public key, the receiver has to obtain the digital signature certificate also.

​