# Is it possible to find plaintext from ciphertext if (n) and (a) are known for RSA?

I have a couple of questions pertaining to a RSA problem. I need to decipher some ciphertext and find out what the original plaintext was.

Modulus: $n = 2537$ and exponent: $a = 11$

Encrypting function: $E(x) = x^{11} \mod 2537$

Using Fermat's Little Theorem to start, I have successfully encrypted some plaintext and decrypted it, so I do know what the other required numbers in this particular RSA system are, however if initially I am only given $n$ and $a$ can I:

1. Mathematically work out some plaintext, if the ciphertext, $n$, and $a$ are known? If so would I basically step through the encryption process in reverse?

2. If not, what is the best/most effective cryptanalysis method to work out what the original plaintext is, if $n$ is relatively small (2537) and $a$ is relatively small (11)?

Note: This is needs to be calculated using the 'maths' behind the system and not a specific computer function.

1. Brute force the private (decryption) exponent. I.e. find the smallest value $b$ such that $(x^a)^b \mod n = x$ for all $x$.