8 bit s box
![8 bit s box 8 bit s box](https://images.ctfassets.net/kvf8rpi09wgk/6Zal2F3OR65GcuajXvt0Gl/4dc90503b300afcea9992c14f3b1971f/Screenshot__78_.png)
The inverse affine transformation is as follows:
![8 bit s box 8 bit s box](https://i.stack.imgur.com/NQunm.jpg)
It is calculated by first calculating the inverse affine transformation of the input value, followed by the multiplicative inverse. For example, the inverse S-box of 0xdb is 0x9f. The inverse S-box is simply the S-box run in reverse. Note that the multiplicative inverse of 0x00 is defined as itself.įor C,C++ here is the initialization of the table: For example, the value 0x9a is converted in to 0xb8 by Rijndael's S-box. Here the column is determined by the least significant nibble, and the row is determined by the most significant nibble. This will generate the following S-box, which is represented here with hexadecimal notation: The value of x will now have the result of the multiplication.Īfter the matrix multiplication is done, exclusive or the value by the decimal number 99 (the hexadecimal number 0圆3, the binary number 1100011, and the bit string 11000110 representing the number in LSb first notation).For three more iterations, repeat steps two and three steps two and three are done a total of four times.Exclusive or the value of x with the value of s, storing the value in x.Rotate the value s one bit to the left if the value of s had a high bit (eighth bit from the right) of one, make the low bit of s one otherwise the low bit of s is zero.
![8 bit s box 8 bit s box](https://slideplayer.com/slide/14080666/86/images/24/The+8+DES+S+Boxes+S-Box+1+S-Box+2+S-Box+3+S-Box+4+S-Box+5+S-Box+7.jpg)
Store the multiplicative inverse of the input number in two 8-bit unsigned temporary variables: s and x.The matrix multiplication can be calculated by the following algorithm: Where is the multiplicative inverse as a vector. This article describes the S-box used by the Rijndael (aka AES) cryptographic algorithm.