Calculator

For the Euclidean Algorithm, Extended Euclidean Algorithm and multiplicative inverse.

Before you use this calculator

If you're used to a different notation, the output of the calculator might confuse you at first.
Even though this is basically the same as the notation you expect. If that happens, don't panic.
Just make sure to have a look the following pages first and then it will all make sense:

• Euclidean Algorithm
     For the basics and the table notation
• Extended Euclidean Algorithm
     Unless you only want to use this calculator for the basic Euclidean Algorithm.
• Modular multiplicative inverse
     in case you are interested in calculating the modular multiplicative inverse of a number modulo n
     using the Extended Euclidean Algorithm

Input

Algorithm

Choose which algorithm you would like to use.

Euclidean Algorithm Extended Euclidean Algorithm Modular multiplicative inverse

Numbers

Enter the input numbers. Note that you need to enter n before b.
E.g. if you want to know the multiplicative inverse of 26 mod 11, then use n=11 and b=26.

n=

b=

Calculate!

Output

This is the calculation for finding the multiplicative inverse of 42 mod 991 using the Extended Euclidean Algorithm:
Answer

So t = 118. Now we still have to apply mod n to that number:
118 mod 991 ≡ 118
So the multiplicative inverse of 42 modulo 991 is 118.

Verification

Let i be the answer we just found, so i=118. We also have b=42 and n=991.
If our answer is correct, then i × b (mod n) ≡ 1 (mod n).
Let's see if that's indeed the case.
i × b (mod n) ≡
118 × 42 (mod 991) ≡
4956 (mod 991) ≡
1 (mod 991)