2k views

### Multiplicative Inverse in AES [duplicate]

I want to calculate the S-box for AES. But I have a problem with the multiplicative inverse step. For example, the inverse of 95 is ...
398 views

### Inversion in $GF(2^8)$ AES [duplicate]

I was wondering how you would calculate the S-box in AES. I found that you have to calculate the inverse of the polynomials in $GF(2^8)$. I found out that to calculate the inverse, you have to use the ...
68 views

### Calculating the inverse for a Rijndael s-box [duplicate]

I want to calculate a Rijndael S-box but something went wrong. How can I calculate the inverse? In the following is my approach: given: $f(x)=x^8+x^4+x^3+x+1 \rightarrow$ binary: 100011011 0x12 = ...
68 views

### How to find multiplicative inverse of a hexadecimal number in the finite field GF(2^8)? [duplicate]

I am new to cryptography. As I was reading a note regarding S-box construction, I found a step mentioning multiplicative inverse of a number in the finite field GF(2^8). I couldn't understand it!! Can ...
22k views

### Multiplication/Division in Galois Field (2^8)

I'm attempting to implement multiplication and division in $GF(2^8)$ using log and exponential tables. I'm using the exponent of 3 as my generator, using instructions from here. However I'm having ...
3k views

### Calculating the multiplicative inverse of a number in $GF(2^n)$ where $n > 8$

Suppose that: We have a polynomial $g(x)$ of degree $n$. $n > 8$. $q$ is the multiplicative inverse of $p$ in $G(2^n)$ modulo $g(x)$. If $p = 0$, then $q = 0$. This could be used: As a non-...
937 views

### How are calculated numbers in AES S-box?

I have a problem calculating the 0x02 value of the AES S-Box. I followed the steps descibed in “How are the AES S-Boxes calculated?”, but my answer is not correct. ...
235 views

### Efficient pen-and-paper calculation of the Galois Field multiplication?

I have been reading on multiplication over GF for the Inverse Matrix Step in AES, and I feel like converting the hex numbers to binary, multiplying them and then doing the modifications required for ...