I am currently preparing for my math exam and the RSA encryption system will be a part of it. But the decryption is quite hard without WolframAlpha or a calculator.
For example I have to decrypt the message $a=3$ which is already encrypted by $e$
The parameter are
- encryption key $e = 151 $
- decryption key $d=7$
To decrypt $a$ you need to solve the following equation
$$3^7\equiv x \ (mod \ 299)$$
According to Wolfram Alpha the solution is 94. Which theorem can I use for this problem. Little Fermat will not work because 299 isn't a prime number. Calculators aren't allowed in the exam.