This document summarizes key aspects of digital signatures and encryption. It explains that digital signatures use public/private key pairs to encrypt messages for authentication, integrity and non-repudiation. A certificate authority acts as a trusted third party by issuing digital certificates that contain a user's public key and identity information signed with the CA's private key. The document also compares features of paper signatures to digital signatures.

1. BY: Rishikesh Somshetti

2. ALICE
ENCRYPTION
PROCESS
PZMSY
DECRYPTION
PROCESS
ALICE

3. Message
Message
“Secret”
Key
ENCRYPT
(LOCK)
(Sender)
Ciphertext
DECRYPT
(UNLOCK)
(Receiver)
Ciphertext

4. Cleartext
Cleartext
Public
Key
Private
Key
ENCRYPT
(LOCK)
Ciphertext
(Sender)
DECRYPT
(UNLOCK)
Ciphertext
(Receiver)

6. •
•
•
Digital Identity that establishes your
credentials when doing business or other
transactions on the Web
Issued by a Certifying Authority (CA)
Contains your name, serial number,
expiration dates, public key, signature of
CA

7. 



Trusted Third Party
An organization which issues public key
certificates
Assures the identity of the parties to whom
it issues certificates
Maintains online access to the public key
certificates issued

8. User Certificate
User
Name &
other
credentials
Certificate
Request
User’s
Public
key
Public
Private
Key pair
Generation
Public
Serial No.
Certificate
Database
User Name
Signed
by using
CA’s
private
key
User’s Email
Address
User’s
Public Key
Publish
License issued
by CCA
User 1 certificate
CA’s Name
Certificate
Class
Validity
Digital
Signature
of CA
User 2 certificate
.
Web site of CA

9. 




Uses secure hash algorithm
Condenses message to 160 bit
Key size 512-1024 bits
Proposed by NIST in 1991
Adopted

10. Hardware tokens
Soft Token
Smart card

11. AUTHENTICATION
INTEGRITY
NONREPUDIATION

12. Paper signatures v/s Digital Signatures
Parameter
Paper
Electronic
Authenticity
May be forged
Can not be copied
Integrity
Signature
independent of the
document
Signature depends
on the contents of
the document
Nonrepudiation
a.
V/s
b.
Handwriting a.
expert needed
Error prone
b.
Any computer
user
Error free

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708/709, Corporate Avenue, Sonawala Lane,
Goregaon East, Mumbai – 400 063.
Ph: +91-22-6139 7100
www.netgainstechnologies.com