Why do we need Digital Signature ???
• A MAC can provide message integrity and
• MAC has a drawback. It needs asymmetric key
that must be establish between the sender
and the receiver.
• A digital signature on the other hand, can use
a pair of asymmetric key (one public and a
What is Digital signature ???
• A digital signature is a mathematical scheme for
demonstrating the authenticity of a digital message or
• A valid digital signature gives a recipient reason to
believe that the message was created by a known
sender , and was not altered in transit.
• Digital signatures are commonly used for software
distribution, financial transactions ,and in cases where
it is important to detect forgery and tampering.
Various methods of employing
Digital Signature:• Using asymmetric ±key Cipher.
• Using Keyed Hash function.
Public key Cryptography
• Public-key cryptography involves the use of
asymmetric key algorithms.
• Asymmetric key algorithms used to create a
mathematically related key pair.
• A secret Private key and a published Public key.
• Protects the confidentiality and integrity of a
• The message is Encrypted using the Public key,
which can only be Decrypted using the Private
Digital Signature using Keyed
• To preserve the integrity of a message.
• The message is passed through an algorithm, called
• T he electronics/equivalent of the document and finger
print pair is the message and digest pair.
• The hashed function creates a compressed image of
the message that can be used as a finger print.
• For compatibility.
• For integrity.
• For efficiency.
Cryptographic protocol or Encryption protocol
It Is an abstract or concrete protocol performing a
security-related function and applies cryptographic
methods. A cryptographic protocol usually incorporates
at least some of these aspects:
Key agreement or establishment.
Symmetric encryption and message authentication
Secured application-level data transport.
Uses of digital signatures
2. Integrity .
Additional security precautions:1. Putting the private key on a smart card.
2. Using smart card readers with a separate
3. Other smart card designs.4. Using digital
signatures only with trusted applications.
• Digital encryption of data is useful during storage and
retrieval of medical history of patients involve dineHealth programs.
• The growth of e-commerce and the recent enactment
of the Electronic Signatures in Global and National
Commerce Act (E-Sign Act)has opened a new frontier.
• With this constant development key management is
becoming an issue.
• Advancements in Hot Java and Java Plug in based
technologies will maintain fluidity and flexibility in key
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