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  1. 1. Cryptography Pradeep…
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  3. 3. ₰ The art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. Only those who possess a secret key can decipher (or decrypt) the message into plain text. ₰ Cryptanalysis is the study of how to crack encryption algorithms or their
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  5. 5. Why do we need Cryptography Security often require that data be kept safe fromunauthorized access. This problem can be broken down into fiverequirements that must be addressed:※ Confidentiality: assuring that private data remains private.※ Authentication: assuring the identity of all parties attemptingaccess.※ Authorization: assuring that a certain party attempting toperform a function has the permissions to do so.※ Data Integrity: assuring that an object is not altered illegally.※ Non-Repudiation: assuring against a party denying a data or acommunication that was initiated by
  6. 6. Basic Concept of
  7. 7. Major CategoriesClassic cryptography Classic cryptography details cryptography styles used in theolden age. It includes simple methods which was used superiorly duringwar times etc. this was before the invention of computers.modern cryptography The development of digital computers and electronics afterWWII made possible much more complex ciphers. Furthermore,computers allowed for the encryption of any kind of data representablein any binary format, unlike classical ciphers which only encryptedwritten language texts; this was new and significant. This was thebeginning of computer
  8. 8. Classic Cryptography (Crypting techniques of olden age)
  9. 9. The main classical cipher types are Transposition ciphers Substitution
  10. 10. Transposition ciphers Transposition ciphers are rearranging the order of letters in a message . • e.g., hello world becomes ehlol owrdl in a trivially simple rearrangement
  11. 11. Substitution ciphers  Substitution ciphers, which systematically replace letters or groups of letters with other letters or groups. e.g., ‘Fly at once becomes gmz bu podf by replacing each letter with the one following it in the Latin
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  13. 13. The development of digital computers and electronics after WWII made possible much more complex ciphers. Furthermore, computers allowed for the encryption of any kind of data representable in any binary format, unlike classical ciphers which only encrypted written language texts; this was new and significant. Computer use has thus supplanted linguisticcryptography, both for cipher design andcryptanalysis. Many computer ciphers can becharacterized by their operationon binary bit sequences (sometimes in groups orblocks), unlike classical and mechanical schemes,which generally manipulate traditional characters(i.e., letters and digits)
  14. 14. The main Modern cipher types are Symmetric-key cryptography Public-key
  15. 15. Symmetric-key cryptography ₰ Symmetric-key cryptography refers to encryption methods in which both the sender and receiver share the same key. ₰ Symmetric-key cryptosystems use the same key for encryption and decryption of a message, though a message or group of messages may have a different key than others. A significant disadvantage of symmetric ciphers is the key management necessary to use them
  16. 16. Public-key cryptography  Whitfield Diffie and Martin Hellman proposed the notion of public-key (also, more generally, called asymmetric key) cryptography in which two different but mathematically related keys are used—a public key and a private key. A public key system is so constructed that calculation of one key (the private key) is computationally infeasible from the other (the public key), even though they are necessarily related. Instead, both keys are generated secretly, as an interrelated
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  18. 18. Cryptanalysis Definition Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key. In non-technical language, this is the practice of codebreaking or cracking the code,
  19. 19. As the cryptography plays an important rolein today’s computer security. The cryptographyalgorithms are highly confidential. And so Wecannot discuss the latest encrypting anddecrypting techniques used my mail servers, socialnetworks and etc.. Though we have several hackers and otherforces were seriously trying to encrypt and decryptthe network
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  21. 21. Applications  Used for security issues.  Used by social networks to provide security  Used to pass messages secretly  Used during war times  Even we can try to pass messages without other’s knowledge about the
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