Digital signature introduction

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this is basic introduction about the Digital Signature

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Digital signature introduction

  1. 1. Digital Signature•Important application of public keyCryptography•Electronic form of Signature•Serves the same purpose as of handwrittensignature but is much secure
  2. 2. Why Digital Signature ? – Authenticate identity of sender – Ensure the original Content of Message – Non-Repudiation – Verifiability by independent, public or third party
  3. 3. Digital Signature
  4. 4. How digital Signature works? User A Transmit via the InternetUse A’s private key to sign the document User B received the document with Verify the signature signature attached by A’s public key stored at the directory User B
  5. 5. Digital Signature Generation and Verification Message Sender Message Receiver Message Message Hash function Hash function Public Key DigestPrivate Encryption DecryptionKey Signature Expected Digest Digest
  6. 6. Certification Authority (CA)• A trusted agent who certifies public keys for general use (Corporation or Bank). – User has to decide which CAs can be trusted.• The model for key certification based on friends and friends of friends is called “Web of Trust”. – The public key is passing from friend to friend. – Works well in small or high connected worlds. – What if you receive a public key from someone you don’t know?
  7. 7. CA model (Trust model) Root Certificate CA Certificate CA CertificateBrowser Cert. Server Cert.
  8. 8. Digital Certificates• Digital Certificate is a data with digital signature from one trusted Certification Authority (CA).• This data contains: – Who owns this certificate – Who signed this certificate – The expired date – User name & email address
  9. 9. Digital Certificate
  10. 10. Digital Signatures (1)Required Conditions:1.Receiver can verify claimed identity of sender.2.Sender cannot later repudiate(deny) contents of message.3.Receiver cannot have concocted message himself.
  11. 11. Digital Signatures (2)• Asymmetric-key signatures• Symmetry-key signatures• Message digests

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