cryptography
- 1. Cryptography Source: Content by William Stallings, Lawrie Brown ,Triad Ltd.
- 2. Introduction to Cryptography Cryptography is the practice and study of techniques for securing communication and data by converting messages into format not understandable by unauthenticated users. Terms: Plain text-Understandable message Cipher – Algorithm to convert plain text to cipher text Cipher text- Scramble form of message only understandable by authenticated users
- 3. Example of Cryptography Suppose you want to send Message –Hello If shift cipher is used for cryptography ,then it shift each character by key value Assume key =3 For Encryption Plain text enryptedcipher text Hello->Khoor(added key of 3 to each char) For Decryption Cipher text decrypted Plaintext KhoorHello(sub key-3 )
- 4. Encryption Encryption is a way of converting data from plaintext to cipher text so that unauthorized parties cannot understand the information. Source:https://www.nodejsera.com/assets/img/encrypt.jpg
- 5. Decryption Decryption is the process of converting ciphertext toplaintext. Source:https://www.nodejsera.com/assets/img/Decrypt.png
- 6. Types of Cryptography Private or Symmetric key cryptography Public or Asymmetric key cryptography
- 7. Private Key cryptography also called as symmetric key cryptography.In symmetric-key cryptography, the same key is used by the sender(for encryption) and the receiver (for decryption). The key is shared. Algorithm: DES,3DES Private Key cryptography
- 8. Private-Key Cryptography traditional private/secret/single key cryptography uses one key Same Key is shared by both sender and receiver Sender uses this key and encryption algorithm to encrypt data Receiver uses this key and decryption algorithm to decrypt data if this key is disclosed communications are compromised also is symmetric, parties are equal hence does not protect sender from receiver forging a message & claiming is sent by sender
- 10. Private-key cryptography Advantages: Simple Faster Disadvantages: Key must exchanges in secure way Easy for hacker to get a key as it is passed in unsecure way.
- 11. An asymmetric-key (or public-key) cipher uses two keys: one private (To encrypt data) and one public(To decrypt data). Asymmetric-key(Public key) cryptography
- 12. Public-Key Cryptography? developed to address two key issues: key distribution – how to have secure communications digital signatures – how to verify a message comes intact from the claimed sender public invention due to Whitfield Diffie & Martin Hellman at Stanford Uni in 1976 known earlier in classified community
- 13. Asymmetric encryption use two keys, one to encrypt the data, and another key to decrypt the data. These keys are generated together One is named as Public key and is distributed freely. The other is named as Private Key and it is kept hidden. Both Sender & Recipient has to share their Public Keys for Encryption and has to use their Private Keys for Decryption.
- 15. Asymmetric encryption use two keys: Public Key - to encrypt the data Private Key - to decrypt the data These keys are generated together. The Public key(s) is distributed freely between the sender and receiver. The other is named as Private Key and it is kept hidden. The Private Key is only used for Decryption and will not be shared between the sender and receiver. Key Points in Asymmetric Encryption
- 16. Merits: Two parties don't need to have their private keys already shared in order to communicate using encryption. Authentication and Non-Repudiation are possible. (Authentication means that you can encrypt the message with my public key and only I can decrypt it with my private key. Non-repudiation means that you can "sign" the message with your private key and I can verify that it came from you with your public key.) De-Merits: Asymmetric Encryption algorithms are comparatively complex. Time consuming process for Encryption and Decryption. MERITS & DE-MERITS
- 17. Public-Key Cryptography Applications can classify uses into 3 categories: encryption/decryption (provide secrecy) digital signatures (provide authentication) key exchange (of session keys) some algorithms are suitable for all uses, others are specific to one
- 19. Comparison between two categories of cryptography