1. Welcome to the Introduction of Digital Signature Submitted By: Ankit Saxena B.Tech. IV year

2. Contents 1 Definition 2 History 3 How a message be send using D.S.
4 Benefits of digital signatures
5 Drawbacks of digital signatures
6 Paper signature Vs Digital signature
7 Conclusion

3. Definition
A digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form. Digital signature schemes normally give two algorithms, one for signing which involves the user's secret or private key, and one for verifying signatures which involves the user's public key. The output of the signature process is called the "digital signature."

4. What’s Digital Signing?
There are many ways to sign a digital document, but we will only present the standard Digital Signing protocol.
Digital signing is used to provide trust that the content has come from the claimed source and has not been altered.
There are many ways to sign a digital document, but we will only present the standard Digital Signing protocol .Digital signing is used to provide trust that the content has come from the claimed source and has not been altered.

5. 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
One cd rom=one tree

6. History
In the famous paper "New Directions in Cryptography", Whitfield Diffie and Martin Hellman first described the notion of a digital signature scheme, although they only conjectured that such schemes existed.Soon afterwards, Ronald Rivest, Adi Shamir, and Len Adleman invented the RSA algorithm that could be used for primitive digital signatures). The first widely marketed software package to offer digital signature was Lotus Notes 1.0, released in 1989, which used the RSA algorithm.

7. How a message be send using Digital Signature

8. WORKING Digital Signature Standard (DSS)

9. Signed Messages OK Sent thru’ Internet Sender Receiver Message if
Calculated
Hash
Message
Sent thru’ Internet
Signed
Message
Message +
signature
Message +
Signature if OK
Signatures
verified
COMPARE
Hash
Hash
SIGN hash
With Sender’s
Private key
Decrypt
Signature
With Sender’s
Public Key
Sender
Receiver

10. Digital Signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
ElGamal
MD5
PGP
S/MIME

11. Public Key Infrastructure (PKI)
Some Trusted Agency is required which certifies the association of an individual with the key pair.
Certifying Authority (CA)
This association is done by issuing a certificate to the user by the CA
Public key certificate (PKC)
All public key certificates are digitally signed by the CA

12. Digital Signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
ElGamal
MD5
PGP
S/MIME

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

14. Digital Signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
DSA
ElGamal
SHA
MD5
PGP
S/MIME

15. RSA A public key crypto system invented by
RIVEST,SHAMIR and ADLEMAN (hence R.S.A. initial) in 1977.
Patented by RSA security but expired in 2000.
It relies on the complexity of factoring very large prime nos.

16. Digital signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
DSA
ElGamal
SHA
MD5
PGP
S/MIME

18. Digital signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
DSA
ElGamal
SHA
MD5
PGP
S/MIME

19. Elgamal It is a public key cryptosystem.
It is not used to encrypt message.
It was invented by Taher Elgamal.
It was not patented.

20. Digital signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
DSA
ElGamal
MD5
PGP
S/MIME

21. MD5
MD5 is another hashing algorithm created by RIVEST of MIT and one of creators of the algorithm. It produces a 128 bit message digest, and while quite popular.

22. Digital signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
ElGamal
MD5
PGP
S/MIME

23. PGP
Pretty Good Privacy(PGP) is one of the most widely used encryption for . It was created by Phil Zimmermann in 1991 and is defined by the open PGP Working Group of the IETF standard RFC PGP is excellent software.

24. Digital signature Technologies
PKI (Public Key Infrastructure)
Digital Certificates
RSA
ElGamal
MD5
PGP
S/MIME

25. S/MIME
S/MIME is based on PKI so it suffers the same problems and high costs. Like PGP, it also just digitally signs the message and doesn’t create legally enforceable electronics signature.

26. Benefits of digital signatures
Authentication :
Digital signatures can be used to authenticate the source of messages. When ownership of a digital signature secret key is bound to a specific user, a valid signature shows that the message was sent by that user. The importance of high confidence in sender authenticity is especially obvious in a financial context.

27. Integrity:
In many scenarios, the sender and receiver of a message may have a need for confidence that the message has not been altered during transmission. Although encryption hides the contents of a message, Furthermore, there is no efficient way to modify a message and its signature to produce a new message with a valid signature, because this is still considered to be computationally infeasible by most cryptographic hash functions

28. Drawbacks of digital signatures
Association of digital signatures and trusted time stamping:
Digital signature algorithms and protocols do not inherently provide certainty about the date and time at which the underlying document was signed. The signer might, or might not, have included a time stamp with the signature, or the document itself might have a date mentioned on it, but a later reader cannot be certain the signer did not, for instance, backdate the date or time of the signature. Such misuse can be made impracticable by using trusted time stamping in addition to digital signatures.

29. Non-repudiation:
In a cryptographic context, the word repudiation refers to any act of disclaiming responsibility for a message. A message's recipient may insist the sender attach a signature in order to make later repudiation more difficult, since the recipient can show the signed message to a third party (eg, a court) to reinforce a claim as to its signatories and integrity.

30. 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
Non-repudiation
Handwriting expert needed
Error prone
Any computer user
Error free
V/s

31. Conclusion
I want to conclude that digital signature is very important for for the Encryption techniques in cryptography , that provides message authenticity and message Integrity.

32. Thank You