What is Digital Signature

1. What is Digital Signature Building confidentiality and trust into networked transactions. Kishankant Yadav www.signyourdoc.com 9571333822

2. Encryption It is a technique of converting plain text into ciphertext and reconverting it into plain text.

3. Basic Techniques of Encryption • Transposition Cipher • Substitution Cipher • Product Cipher

4. Basic Techniques of Encryption- Transposition Cipher Encrypts by changing the order of characters in the text. • e.g. : Replace 1st character with 6th • 2nd with 7th • 3rd with 8th • 4th with 9th • 5th with 10th and so on

5. Basic Techniques of Encryption- Transposition Cipher WE WILL ATTACK ON BHAI ON SUNDAY TRANSPOSE LL ATWE WI ON BHTACK SUNDAAI ONY

6. Basic Techniques of Encryption- Substitution Cipher Encrypts by replacing the characters in the text with characters in a “Key” on the basis of some rule. e.g. : • Key is “MANISH” and Rule is Replace all • A in the text with M • B with A • C with N • D with I • E with S • F with H • G with A and so on

7. Basic Techniques of Encryption- Substitution Cipher INDORE IS A GOOD CITY SUBSTITUTE DKILQS DR M BLLI NDTY

8. Basic Techniques of Encryption- Product Cipher Combination of Transposition and Substitution • Take a Key • replace the characters in the text with characters in the Key. • Transpose the result.

9. Basic Techniques of Encryption- Product Cipher INDORE IS A GOOD CITY SUBSTITUTE DKILQS DR M BLLI NDTY TRANSPOSE S DR DKILQI NDTM BLLY

10. Elements of Encryption Decryption method Encryption method Plain text Plain text Encryption key Decryption Key Cipher text • Encryption Algorithm (function used to encrypt or decrypt) • Encryption keys (information used to cipher)

11. Good Encryption System: Features • Short Key • Strong Algorithm • High work factor • Low error propagation

12. Encryption Building confidentiality and trust into networked transactions. CHANGING THE WAY OF DOING BUSINESS

13. Using Encryption A MATTER OF TRUST • Building Trust: Direct trust relationship

14. Credit Card Notarized NotarizedDocument MedicalRecords Contract Some every day transactions: Why do we place trustin these transactions? • Authentication • Confidentiality • Integrity • Non-repudiation

15. Ways of Encryption Symmetric Key or Private Key Encryption Asymmetric Key orPublic Key Encryption (abbreviated as PKI) Two ways of encryption

16. Symmetric Cryptosystem DES | RC4 DES | RC4 Four score and seven years ago, our forefathers brought forth the proposition sdfklj98a475$56jhgv98456vjnf84576FGHH78lfkghj-506#6lkjg4#$5;lkn;t7;lsk%0 Four score and seven years ago, our forefathers brought forth the proposition Cleartext Message Cipher Text Cleartext Message Also called private key infrastructure

17. Symmetric Cryptosystem Original Message Encrypted Message Original Message Encrypted Message Also called private key infrastructure • Similar key is used for encryption and decryption • Both parties should know the same key Secured transmission of encryption key to other person is a problem.

18. Asymmetric Cryptosystem • Also called Public Key Infrastructure (PKI) • Improvement over Private Key System • Provides all elements expected from a secure transaction : • Authentication • Confidentiality • Integrity • Non-repudiation • Accordingly generates : • Signed message • Secret message • Signed and Secret message

19. Decryption Encryption Recipient’s Public Key Recipient’s Private Key Public Key System One half of a key pair is used to encrypt, the other half is used to decrypt.

20. Public Key Infrastructure(PKI) Basic Methodology • Uses a pair of keys. • One part of pair is used for encryption • Another part is used for decryption • One part is kept private (called private key of a person) and another is made public (called public key of a person) • Any key (public or private) can be used for encryption and then another is used for decryption • Same key can not be used for encryption and decryption both. There has to be combination of both keys.

21. Public Key Infrastructure(PKI) Encryption Original Message Encrypted Message Receiver’s public key Receiver’s private key Encrypted Message Original Message Decryption How messages are generated To generate a secret message • Message is encrypted by sender with Receiver’s public key and • It is decrypted by receiver with his private key. It ensures : • Confidentiality • Integrity

22. Public Key Infrastructure(PKI) Encryption Original Message Encrypted Message Sender’s private key Sender’s public key Encrypted Message Original Message Decryption How messages are generated To generate a signed message • Message is encrypted by sender with Sender’s private key and • It is decrypted by receiver with Sender’s public key. It ensures : • Authentication • Non Repudiation

23. Asymmetric Cryptosystem Original Message Encrypted Message I Encrypted Message II Receiver’s public key Sender’s private key Encrypted Message I Encrypted Message II Original Message Receiver’s private key Sender’s public key How messages are generated To generate a signed and secret message : • Message is first encrypted by sender with Sender’s private key. • This encrypted message is again encrypted with Receiver’s public key • It is decrypted by receiver first with his private key and then with sender’s public key. It ensures : Confidentiality Integrity Authentication Non Repudiation

24. Digital Signatures Basic Methodology • Digital signatures are hash code of a document encrypted with sender’s private key. • For sending the message, first hash code of message is generated. • This hash code is encrypted using sender’s private key. • The message is sent along with encrypted hash code. • At other end, receiver decrypts hash code with sender’s public key. • He also on his own calculates hash code of the message received. • Two hash codes should tally. It ensures : Integrity Authentication Non Repudiation

25. Digital Signatures • In earlier process, message has been sent in clear text form thus confidentiality has not been achieved. • To overcome this problem, message and encrypted hash code may be encrypted by a symmetric key. • This symmetric key is also then encrypted with receiver’s public key. • All these i.e. Message and encrypted hash code which are now encrypted with symmetric key and symmetric key itself which is now encrypted with receiver’s public key, are sent to receiver. • Receiver first decrypt the symmetric key with his private key and then decrypt message and hash code with this symmetric key.

26. Digital Signature Sender’s Private Key Hash Code Original Message Original Message Recipient’s Public Key Symmetric Key Encrypted Symmetric Key Encrypted & Signed Sender How does PKI work?

27. Recipient’s Private Key Recipient Encrypted Symmetric Key Symmetric Key Hash Algorithm Message verified Original Message Hash Code Sender’s Public Key Digital Signature Encrypted & Signed How does PKI work?

28. private Digital Certificate A Digital Certificate is a digitally signed document that associates a public key with a user. Certificate ties a participant to public key Public Key: Name: Prashant Mali ID Number & Name Number: 2564567A Expires:31December 2022 Validity Period The authenticity of the certificate is guaranteed by the digital signature generated using the CA’s private key. Signed: CA’s Signature

29. Key Generation Certificate Issuance or Certificate Validation Key Usage Key Expiry Key Update Key Lifecycle Management

30. Encryption Standard Data Encryption standard • A short key, strong algorithm system • Uses a 64 bit key, 56 bits for algorithm and 8 bits are parity RSA (Rivest, Shamir, Adalman) • Public key system. • Once private key is used to encrypt, it can be decrypted only using its public key and vice-versa.

31. Thank You Questions Contact: www.signyourdoc.com Kishan.kant03@gmail.com Cell: 9571333822