1. Message Digest &
Digital Signature.
Presented By
 Lamack Jose (Roll No 16)
 Dinesh Kodam (Roll No 34)
 Manoj Patil (Roll No 36)

2. Concept of Hash (Message
Digest)
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3. Concept of Hash (Message
Digest)
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4. Idea of a Message Digest
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5. Idea of a Message Digest
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6. Requirement of a Message
Digest
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7. Message Digest
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8. Digital Signatures
farhan.mohd@yahoo.co.in
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9. Digital Signatures
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10. Digital Signatures
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11. Steps for the process
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12. Digital Signatures
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13. The Sender’s Side
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14. The Receiver’s Side
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15. Properties of Digital Signatures
•
Digital signature does not provide
privacy. If there is a need for
privacy, another layer of
encryption/decryption must be
applied.
•
1.
2.
3.
Digital signatures can provide
Integrity,
Authentication, and
Nonrepudiation.
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16. Properties of Digital Signatures
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17. Properties of Digital Signatures
1.
2.
Integrity The integrity of a message is
preserved because if Eve intercepted the
message and partially or totally changed it,
the decrypted message would be
unreadable.
Authentication We can use the following
reasoning to show how a message can be
authenticated. If Eve sends a message while
pretending that it is coming from Alice, she
must use her own private key for encryption.
The message is then decrypted with the
public key of Alice and will therefore be
nonreadable. Encryption with Eve's private
key and decryption with Alice's public key
result in garbage.
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18. Properties of Digital Signatures
3.
Nonrepudiation Digital signature also provides for
nonrepudiation. Bob saves the message received
from Alice. If Alice later denies sending the
message, Bob can show that encrypting and
decrypting the saved message with Alice's private
and public key can create a duplicate of the
saved message. Since only Alice knows her
private key, she cannot deny sending the
message.
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