●“A Digital Signature is an
Electronic Signature .”
To authenticate the identity of the sender of a
The signer of a document, and
To ensure that the original content of the message
or document that has been signed is unchanged
●Only the owner can create the digital signature,
hence it can be used to verify who created a
●Generally don't sign the whole message
(doubling the size of information exchanged), but
just a digest or hash of the message
●A hash function takes the message, and
produces a fixed size (typically 64 to 512 bits)
value dependent on the message
●Digital Signature - a data string which associates
a message with some originating entity
●When using a digital signature, the data itself is
not encrypted, but a hash of the data is
encrypted with a private key. A hash (also
known as a digest) is a unique, fixed-length
mathematical value that is determined by the
content of the message
●In 1976,Whitfield Diffie and Martin Hellman first
described the Digital Signature.
●In 1984, Shafi Goldwasser, Silvio Micali, and
Ronald Rivest became the first to define the
security requirements of digital signature
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●These are digital signatures of same person on different
●Digital Signatures are numbers
●Same Length – 40 digits
●They are document content
Sent thru’ Internet
●A digital certificate is an electronic “document”
●or computer generated record that officially links
together the subscriber’s identification with the
corresponding public key.
●The certificate is digitally signed by the issuing
Certification Authority (CA ) to ensure the
certificate’s authenticity so that anyone in
possession of the CA’s public
key can verify the legitimacy of the certificate
●Certificate authorities (CA’s) will provide a requestor
with someone’s public key contained in a certificate.
Information in the certificate will identify the public
key’s owner, and provide the name of the CA who
validated the identity and signed the identity to public
key binding. In this way it is possible to see that a
certificate serves as a kind of protective “container”
for the public key, protecting the integrity of its
binding to an owner and authenticating both the
binding and identity via the reputation (and trust) of
the signing CA.
Private Key – Used for making digital signature
Public Key – Used to verify the digital signature
●If the sender wishes to prove to a recipient that
he or she is the source oftheinformation, the
sender uses his or her private key to digitally
sign a message (adigital signature).
●The receiver of a digitally signed message uses
the sender’s public key to verify the signature so
that the receiver knows that the person
controlling the private key corresponding to the
public key sent the information, and that the
received information has not been altered since
it was signed.
●A key generation algorithm that selects a private
key uniformly at random from a set of possible
private keys. The algorithm outputs the private
key and a corresponding public key.
●A signing algorithm which, given a message and
a private key, produces a signature.
●A signature verifying algorithm which given a
message, public key and a signature, either
accepts or rejects.
●To provide Authenticity, Integrity and
Non-repudiation to electronic
●To use the Internet as the safe and
secure medium for e-Commerce.
●Authentication :-Although messages may often
include information about the entity sending a
message, that information may not be accurate.
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
1.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, it may be
possible to change an encrypted message
●Putting the private key on a smart card
●Using smart card readers with a separate
●Using digital signatures only with trusted
●Saving Of Time
●Digital signatures are commonly used for
software distribution, financial transactions, and
in other cases where it is important to detect
forgery and tampering.
●Hence We are conclude that to use digital
signature we can secure our information by
Private and public key.
● A digital signature is an electronic signature that
can be used to authenticate the identity of the
sender of a message or the signer of a