A straightforward test of encrypting and decrypting an eight-letter message with the Vigenère Cipher using a four-letter key.  Message letters are generated uniformly at random from the English alphabet, as are the key letters.  Students are expected to be able to map English letters onto elements of $\mathbb{Z}_{26}$ in the usual order.

A straightforward test of encrypting and decrypting an eight-bit message with the Vernam Cipher.  The message and the key are uniform and independently generated eight-bit strings.

A straightforward test of encrypting and decrypting an eight-letter message with the Substitution Cipher.  Message letters are generated uniformly at random from the English alphabet and the key is a uniformly chosen random permutation of the alphabet.  Students are expected to be able to map English letters onto elements of $\mathbb{Z}_{26}$ in the usual order.

The purpose of this question is to ask the students to go through one Rijndael round from the AES algorithm.

A straightforward test of encrypting and decrypting an eight-letter message with the Caesar Cipher.  Message letters are generated uniformly at random from the English alphabet, as is the key.  Students are expected to be able to map English letters onto elements of $\mathbb{Z}_{26}$ in the usual order.

Part of HELM Book 1.4.2

The exercises for HELM Book 1.4.1

The 7th task in HELM book 1.4 section 1.

The 6th task in HELM book 1.4 section 1.

The 5th task in HELM book 1.4 section 1.

The 4th task in HELM book 1.4 section 1.

The 3rd task in HELM book 1.4 section 1.

The 2nd task in HELM book 1.4 section 1.

The first task in HELM book 1.4 section 1.

HELM Book 1.3.1 exercises

Factorise a quadratic, x^2+bx+c. An exam can choose whether or not a=1. Part of HELM Book 1.3

Factorise a quadratic, ax^2+bx+c. An exam can choose whether or not a=1. Part of HELM Book 1.3

Factorise a quadratic. Part of HELM Book 1.3

Factorise a quadratic. Part of HELM Book 1.3

HELM Book 1.3.5 exercises

Factorise the difference of two squares, t^2-number^2. Number is a random perfect square, or 1 over a perfect square.

The purpose of this question is to ask the students to go through one Rijndael round from the AES algorithm.

This question runs the students through the Elliptic Curves version of Diffie Hellman.

In this question the students are given the public and private keys for El Gamal through Elliptic Curve and a message to decrypt. They have to decrypt the message.

HELM Book 1.3.4 exercises

Explain why one variable is a factor but the other is not. Factorise the expression, whose factor is alphanumeric. Part of HELM Book 1.3

Factorise a 2-term expression where the gcd can be alphanumeric. Part of HELM Book 1.3

Factorise an expression of 2 or 3 terms where the gcd is a letter times a number. Part of HELM Book 1.3.4

Expand (a+b)(c+d). a,b,c,d are random terms that can be +ve or -ve, and can consist of a number and/or a letter.

The answer must contain no brackets but will be accepted if it is not simplified from there.

Part of HELM Book 1.3

Solving $\cos(nx)=a$ for $x\in (0,\pi)$, where $n$ is an integer and $a\in(0,1)$.