Data Encryption

By khayam SarhadiRoll No: 130221

BS-CS 7th UOS

Encryption Definition:The action of hiding 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.

A message is clear text (plaintext) is encrypted (disguised) through the use of an encryption key to create a Cipher text.

In symmetric (Single key):The encryption and decryption keys are the

same.

In asymmetric (two keys):The encryption and decryption keys are

different.

Encryption Methods:Encryption is skilled by scrambling( ال4ٹ پل4ٹ

the bits, characters, words, or phrases (کرناin the original message. Scrambling involves two activities:

Transposition (ہجگ کی تبدیلی ) Substitution (قائم مقام)

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.

Data Encryption Standard (DES):Most widely used algorithmFounded by IBM It is symmetric cryptosystemDeveloped to protect sensitive, unclassified,

US government, Computer data.Used to provide authentication of electronic

funds transfer messages.

The basic process in enciphering a

64-bit data block 56-bit key using the

DES consists of: An initial permutation (IP) 16 rounds of a complex

key dependent calculation f

A final permutation, being the inverse of IP

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 (L0) 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.

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 proposedRSA algorithm is considered to be highly

secure.

Tayyab Arif 00923445064252, Allama Iqbal Open University

Public key encryption can achieved:

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