1. Digital Signatures

2. PRESENTED BY
SINDHU PRIYA.S
II-YEAR ECE
113011013827

3. 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

4. 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

5. Digital Signatures
Each individual generates his own key pair
[Public key known to everyone & Private key only to the owner]
Private Key – Used for making digital signature
Public Key – Used to verify the digital signature

6. How it works
 The use of digital signatures usually involves two
processes, one performed by the signer and the other
by the receiver of the digital signature:
 Digital signature creation uses a hash result derived
from and unique to both the signed message and a
given private key. For the hash result to be secure,
there must be only a negligible possibility that the
same digital signature could be created by the
combination of any other message or private key.
 Digital signature verification is the process of checking
the digital signature by reference to the original
message and a given public key, thereby determining
whether the digital signature was created for that same
message using the private key that corresponds to the
referenced public key.

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

9. 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
a. Handwriting
expert needed
b. Error prone
a. Any computer
user
b. Error free
V/s

10. Public Key Cryptography
Encryption Technologies
DocumentDocumentDocumentDocument DocumentDocumentDocumentDocumentEncryptedEncrypted
DocumentDocument
EncryptedEncrypted
DocumentDocument
EncryptedEncrypted
DocumentDocument
EncryptedEncrypted
DocumentDocument
Public Key of B
Confidentiality
Private Key of B

11. E-Governance
 Empowering Citizens
a) Transparency
b) Accountability
c) Elimination of Intermediatory
d) Encouraging Citizens to exercise their Rights