Cryptography is the science of secure communication. It uses techniques like encryption to provide confidentiality, integrity, and authentication of information. The main goals of cryptography are to ensure that information is hidden from unauthorized parties and to verify the identity of senders and the authenticity of messages. Modern cryptography uses both symmetric and asymmetric algorithms, with public key cryptography being widely used to securely exchange keys and for functions like digital signatures. Common cryptographic techniques include encryption, hashing, digital signatures, and digital certificates. Cryptography has many applications including e-commerce, network security, and communication security.

1. CryptographyMade by:-Shray Jali

2. CryptographyCryptology is the science of secure communications

3. Formed from the Greek words kryptós, "hidden", and logos, "word".

4. Cryptography is a framework of methodologies used to ensure the CIA triad for our information C –Confidentiality I –Integrity A -AuthenticityCryptography was known anciently as Encryption which means: Hiding the information from unauthorized entities.

5. It could be implemented manually, mechanically or even electronically encryptionProcess by which a message is transformed into another message using a mathematical function and a special encryption password.

6. If we are using symmetric encryption, then we will encrypt the clear message with one key and decrypt it with the same keysymmetric encryptionWe will use 9 different private keys for achieving bidirectional communication between XYZ and ABC

7. We need to define a way by which we can exchange these private keys in a secure manner between distant entities

8. DES, 3DES, Blowfish, IDEA, RC5, Safer, Serpent and AES are the well known symmetric encryption algorithmsasymmetric encryptionIf we are using asymmetric encryption, then we will encrypt the clear message with one key and decrypt it with a different keyasymmetric encryptionABC and XYZ have their public keys distributed over each other, anyone needs to talk to the other will use the other’s public key to encrypt the traffic and the other will use his own private key to decrypt the traffic, X will use A’s public key to encrypt clear traffic A will receive the cipher to decrypt it using his own private key

9. RSA is the famous asymmetric key encryption algorithmEarly Cryptography3500 BC: SumeriansCuneiform writings

10. Early Cryptography500- 600 BC486 BC: Greece60 –50 BC: JuliusCaesarSubstitution cipherUsed by HebrewShift letters by X positions E.g. X = 3: A -> D, B -> E, C ->F, ..

11. Medieval Cryptography1845: Morse code1918: The ENIGMA26 letter keyboard forinput & each lamp for a key

12. “Scrambler”Medieval CryptographySubstitution ciphersubstitutes each letter by another letter to diguise it plain text: a b c d e f g h i j k l m n o p q r s t u v w x y z Cipher text: q w e r t y u i o p a s d f g h j k l z x c v b n mTransposition CipherThe Ciphertext is formed by re-arranging the Plaintext in the form of a matrix and then transposing it.modern Cryptography1918: ADFGVX Cipher

13. modern Cryptography1976: Diffie-Hellman Key ExchangePrivate key: This key must be know only by its owner.Public key: This key is known to everyone

14. modern Cryptography1977: RSA: Rivest, Shamir & Adleman AlgorithmBoth public and private key are interchangeable

15. Variable Key Size (512, 1024, or 2048 bits)

16. Most popular public key algorithmmodern Cryptography1991: Pretty Good Privacye-mail security

17. Uses a block cipher called IDEA

18. Uses Digital Signatures

19. Uses Web Trust

20. E.g. X.509 certificates in SSL modern CryptographyBlock CiphersSymmetric-key encryption algorithm that changes a fixed length of block text into same length of Cipher text

21. Encryption works by means of key and Decryption is the reverse of encryption process using the same keyThe Data Encryption Standard (DES) and the Advanced Encryption Standard (AES) are block cipher designs which are used across a wide range of applications, from ATM encryption to e-mail privacy and secure remote accessStream CiphersGenerates a keystream & combines with plaintext to form ciphertext, e.g. RSA’s RC4

22. Suitable for online encryption of data, e.g. Encrypting Voice Comms

23. Much faster than block ciphers for online workmodern CryptographyPublic key cryptographyThey use different keys for encryption and decryption.

24. Encryption operates on plaintext using the encryption key and the modulus to produce cipher text