SUBSTITUTION BOXES (S-BOX)




  • In cryptography , a S-box is a basic component of symmetric key algorithm, which performs substitution . In block cipher, they are typically used to obscure the relationship between the key ciphertext.
  • The S-boxes carry out the real mixing (confusion).
  • It takes in m number of input bits and gives out m bits of output where m and n are not equal.
  • DES uses 8 S-boxes each with a 6-bit input and 4-bit output.
  • Each S-box is actually 4 little 4 bit boxes.
  • outer bits 1 &6 are known as row bit.
  • inner bit 2 & 5 are known as column bit.



                                     













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