# Algebra and Cryptography

Course: CSE3230 Edition: 2020-2021

**Mon, Jun 28, 2021 12:00:00**

#### Resit Exam - S-box Construction question

at Mon, Jun 28, 2021 10:58:45 updated at Mon, Jun 28, 2021 10:59:16For the S-box question, you can get values that are not defined (like \(\frac{1}{0}\)). In such cases, you are free to select any value for that specific S-box output.

#### Resit Exam - SageMath question

at Mon, Jun 28, 2021 10:51:16In one group, for question 2b, here is the correction:

Define the field extension \(F_{2^5}\) over \(F_2\) using the primitive polynomial. Find the additive and the multiplicative representations for the elements of \(F_{2^5}\). (3 points)

#### Resit Exam - S-box Construction question

at Mon, Jun 28, 2021 10:30:57Please consider \(F(0) = 0\) for \(x=0\).

#### Resit Exam - Boolean Function Construction question

at Mon, Jun 28, 2021 09:37:05The value for the exponent \(d\) is not defined by the assignment, you can freely select the value, but it must be different from 1.

#### Resit Exam - Typo fixed in Proof question

at Mon, Jun 28, 2021 09:16:27The initial version of the proof question contained a small typo in the definition of f, being \( f(x_1,\cdots,x_{n+1}) = g(x_1,\cdots,x_n) \oplus x_n \) instead of \( f(x_1,\cdots,x_{n+1}) = g(x_1,\cdots,x_n) \oplus x_{n+1} \). The typo has now been fixed.