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Digital Signature


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Digital Signature

  2. 3. ENCRYPT ( LOCK ) Message Ciphertext “ Secret” Key DECRYPT ( UNLOCK ) Ciphertext Message (Sender) (Receiver)
  3. 4. ENCRYPT (LOCK) Cleartext Ciphertext Public Key DECRYPT (UNLOCK) Ciphertext Private Key Cleartext (Sender) (Receiver)
  4. 6. <ul><li>Digital Identity that establishes your credentials when doing business or other transactions on the Web </li></ul><ul><li>Issued by a Certifying Authority (CA) </li></ul><ul><li>Contains your name, serial number, expiration dates, public key, signature of CA </li></ul>
  5. 7. <ul><li>Trusted Third Party </li></ul><ul><li>An organization which issues public key certificates </li></ul><ul><li>Assures the identity of the parties to whom it issues certificates </li></ul><ul><li>Maintains online access to the public key certificates issued </li></ul>
  6. 8. Signed by using CA’s private key User Name & other credentials User’s Public key User Certificate Certificate Database Publish Certificate Request Key pair Generation Private Public Web site of CA User 1 certificate User 2 certificate . Public License issued by CCA User Name User’s Public Key CA’s Name Validity Digital Signature of CA Certificate Class User’s Email Address Serial No.
  7. 9. <ul><li>Uses secure hash algorithm </li></ul><ul><li>Condenses message to 160 bit </li></ul><ul><li>Key size 512-1024 bits </li></ul><ul><li>Proposed by NIST in 1991 </li></ul><ul><li>Adopted </li></ul>
  8. 10. Soft Token Hardware tokens Smart card
  9. 12. Paper signatures v/s Digital Signatures V/s 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 <ul><li>Handwriting expert needed </li></ul><ul><li>Error prone </li></ul><ul><li>Any computer user </li></ul><ul><li>Error free </li></ul>