Data Encryption Standard DES):
 DES uses both transposition and substitution and for that reason sometimes referred as product cipher its input,output and key are 64 bit long the set of 64 bits referred as blocks
 The Cipher consisting of 16 rounds or iteration . Each round uses separate key of 48 bits
 DES encryption algorithm is the first 64 bits plain text uses through initial permutation(IP) that rearrange the bits to produce permitted input .
Then there is a phase consisting of 16 rounds of the same function which involves both permutation and substitution technique functions. The output of 16 round consisting of 64 bits that are function opf input plain text and key
 The left and right half of the are swapped to produce the preoutput atleast the preoutput is passed through a permutation.(IP) . i.e,the inverse of initial permutation to produce the 64 bit cipher text.
INITIAL PERMUTATION:
 The initial permutation and its inverse the input to the table consists of 64 bits numbered from 164.
 The 64 entries in the permutation table contain the permutation of the numbers from 164 each entry in the permutation indicates the position of numbered input bit in the output which also contains 64bits as the output.

The over all processing at each round can be summarized in the following
Li=Ri1
Ri=liF*(Ri1,Ki)
 The left output li is the copy of right input Ri1
 The right output Ri is the XOR of left input Li1 and right input Ri1and key Ki
 The substitution and permutation both functions are used.
SUBSTITUTION box:
 It is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext
 The 48 bit input block is divided into 8sub blocks and each sub block is given to a sbox . The Sbox transforms the 6bit input 4bit output.
 A two bit binary number to select one of the 4 substitutions defined by the four rows in the table the two bits can store any decimal between 03 this specifies row number the middle 4 bits selects one of the 16 columns.
Key Generation:
64 bit key is used as the input to the algorithm the initial 64bit key is transformed into 56bit the key by discarding every 8th bit of a initial key.
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Data Encryption Standard DES):
 DES uses both transposition and substitution and for that reason sometimes referred as product cipher its input,output and key are 64 bit long the set of 64 bits referred as blocks
 The Cipher consisting of 16 rounds or iteration . Each round uses separate key of 48 bits
 DES encryption algorithm is the first 64 bits plain text uses through initial permutation(IP) that rearrange the bits to produce permitted input .
Then there is a phase consisting of 16 rounds of the same function which involves both permutation and substitution technique functions. The output of 16 round consisting of 64 bits that are function opf input plain text and key
 The left and right half of the are swapped to produce the preoutput atleast the preoutput is passed through a permutation.(IP) . i.e,the inverse of initial permutation to produce the 64 bit cipher text.
INITIAL PERMUTATION:
 The initial permutation and its inverse the input to the table consists of 64 bits numbered from 164.
 The 64 entries in the permutation table contain the permutation of the numbers from 164 each entry in the permutation indicates the position of numbered input bit in the output which also contains 64bits as the output.

The over all processing at each round can be summarized in the following
Li=Ri1
Ri=liF*(Ri1,Ki)
 The left output li is the copy of right input Ri1
 The right output Ri is the XOR of left input Li1 and right input Ri1and key Ki
 The substitution and permutation both functions are used.
SUBSTITUTION box:
 It is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext
 The 48 bit input block is divided into 8sub blocks and each sub block is given to a sbox . The Sbox transforms the 6bit input 4bit output.
 A two bit binary number to select one of the 4 substitutions defined by the four rows in the table the two bits can store any decimal between 03 this specifies row number the middle 4 bits selects one of the 16 columns.
Key Generation:
64 bit key is used as the input to the algorithm the initial 64bit key is transformed into 56bit the key by discarding every 8th bit of a initial key.