article
Public Key Cryptography
An introduction to coding and decoding messages and the maths behind how to secretly share information.
Indices
problem
Age of Augustus
Age
11 to 14
Challenge level
The English mathematician Augustus de Morgan has given his age in algebraic terms. Can you work out when he was born?
problem
Maundy Money
Age
11 to 14
Challenge level
How much money did the Queen give away in pence as a power of 2?
problem
Negative Power
Age
14 to 16
Challenge level
What does this number mean ? Which order of 1, 2, 3 and 4 makes the
highest value ? Which makes the lowest ?
problem
Tens
Age
16 to 18
Challenge level
When is $7^n + 3^n$ a multiple of 10? Can you prove the result by two different methods?
problem
Elevens
Age
16 to 18
Challenge level
Add powers of 3 and powers of 7 and get multiples of 11.
problem
Largest Expression
Age
14 to 16
Challenge level
Which of these five algebraic expressions is largest, given $x$ is between 0 and 1?
problem
Powerful Zeros
Age
14 to 16
Challenge level
How many zeros are there at the end of $3^4 \times 4^5 \times 5^6$?
problem
Perfectly Square
Age
14 to 16
Challenge level
The sums of the squares of three related numbers is also a perfect square - can you explain why?
problem
The Public Key
Age
16 to 18
Challenge level
Find 180 to the power 59 (mod 391) to crack the code. To find the
secret number with a calculator we work with small numbers like 59
and 391 but very big numbers are used in the real world for this.