# RSA/cryptography question

• Nov 10th 2013, 10:39 AM
euphony
RSA/cryptography question
I'm given a specific number (say n) to use "as an encryption key," and I have to find the decryption key.

Is n the same as the encryption exponent?
• Nov 10th 2013, 10:54 AM
SlipEternal
Re: RSA/cryptography question
• Nov 10th 2013, 01:37 PM
euphony
Re: RSA/cryptography question
So is the encryption key the same as the public key exponent e? The number I'm supposed to use as an encryption key is even, and it seems like it can't be the public key exponent because phi(m)=(p-1)(q-1) is also even.
• Nov 10th 2013, 01:48 PM
SlipEternal
Re: RSA/cryptography question
It sounds like you are given $\displaystyle m$, not $\displaystyle e$. So, you need to find $\displaystyle \varphi(m)$. Then the decryption key would be $\displaystyle e^{-1} \pmod{\varphi(m)}$? I dunno.
• Nov 10th 2013, 01:53 PM
SlipEternal
Re: RSA/cryptography question
Oh, just read through the link I sent you. It tells you precisely what to do in the section titled "A working example".
• Nov 10th 2013, 07:42 PM
euphony
Re: RSA/cryptography question
Is there any way to use an even number as an encryption exponent?