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# Data Encryption

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### Data Encryption

1. 1. Data Encryption Arvind Rana Lecturer Computer Science SVSD PG College Bhatoli, Distt Una, H.P.
2. 2.  Encryption Definition:  The action of disguising information so that it can be recovered easily by the persons who have the key, but is highly resistant to recovery by persons who do not have the key. Arvind Rana, Lecturer Computer Science
3. 3. A message is cleartext (plaintext) is encrypted (disguised) through the use of an encryption key to create a Ciphertext. Arvind Rana, Lecturer Computer Science
4. 4.  The encryption key may be changed from time to time to make an intruder’s task more difficult.  Restoration of a ciphertext to cleartext is achieved by the action of decryption using a decryption key. Arvind Rana, Lecturer Computer Science
5. 5.  In symmetric (Single key):  The encryption and decryption keys are the same.  In asymmetric (two keys):  The encryption and decryption keys are different. Arvind Rana, Lecturer Computer Science
6. 6.  Encryption Methods:  Encryption is accomplished by scrambling the bits, characters, words, or phrases in the original message. Scrambling involves two activities:   Transposition Substitution Arvind Rana, Lecturer Computer Science
7. 7.  Transposition:  In which the order of the bits patterns, characters, words or phrases is rearranged.  Substitution:  In which new bit patterns, characters, words, or phrases are substituted for the originals without changing their order. Arvind Rana, Lecturer Computer Science
8. 8.  Data Encryption Standard (DES):  Most widely used algorithm  Pioneered by IBM  It is symmetric cryptosystem  Developed to protect sensitive, unclassified, US government, Computer data.  Used to provide authentication of electronic funds transfer messages. Arvind Rana, Lecturer Computer Science
9. 9.  DES Algorithm:  The algorithm accepts plaintext, P, and performs an initial permutation, IP, on P producing P0, The block is then broken into left and right halves, the Left (L 0) being the first 32 bits of P0 and the right (R0) being the last 32 bits of P0.  With L0 and R0, 16 rounds are performed until L16 and R16 are generated.  The inverse permutation, IP-1, is applied to L16R16 to produce ciphertext C. Arvind Rana, Lecturer Computer Science
10. 10.  Public Key Cryptosystem  It is an asymmetric cryptosystem.  First announced in 1976.  Offer a radically different approach to encryption.  The idea depends on the use of a pair of keys that differ in a complementary way.  Several algorithms are proposed  RSA algorithm is considered to be highly secure. Arvind Rana, Lecturer Computer Science
11. 11.  Public key encryption can achieved:  Privacy  Authentication
12. 12. Arvind Rana Lecturer Computer Science SVSD PG College Bhatoli, Distt. Una, H.P.