How Prime Numbers Create Online Banking Security

We had some fun trying to understand how prime numbers are used for online security banking. 

Last week, quite a lot of us had chosen to learn about that as one of our home learning choices.

We began by watching two YouTubes ( YouTube 1 YouTube 2 )and after each we discussed with our partner what we understood and made notes on the images provided:

From this we had some great discussions how prime numbers are used with online banking and how prime numbers help prevent our accounts being hacked into.

We thought it was fascinating that it is estimated to take over 1000 years for a hacker to be able to encrypt the code that banks use for our credit cards etc.

To help us gain a sense of WHY it is so difficult, we were posed with this problem:

The composite number to access the bank account is 1 591.

Which two prime numbers (below 100) are the keys when multiplied to create that composite number?

We had a stopwatch displayed.

If someone was able to find the two prime numbers, they recorded the time it took them to 'crack' it and access the money.

Even though we had our prime number hundred grids with us, we found it really challenging.  Only one of us was able to find the two primes in 10 minutes (when we decided to give up).

Some children chose 2 prime numbers, that when multiplied, came close to the composite, but even then it was difficult to work out.

So, what did we discover from this?

- It IS really difficult!

- This was hard with primes below 100; imagine how hard it would be with those massive prime numbers we discovered!

- I can see now why using primes is a great way to protect our money online.

We looked again at the currently largest know prime number and were blown away by thinking how difficult it would be to do this with numbers that large:

It was then their turn to create an online banking encryption. 

They chose 2 prime numbers below zero, multiplied them and found what the composite answer is.

They gave the composite number to a partner who needed to try to hack into their bank security system.

Again, only 1 student had managed to do it within 10 minutes.

We were all really excited about trying to hack in and it was clear that we all gained a sense of why using prime numbers as private keys is a great choice to protect our money online.