Cryptography help.

[RealGiganitris]

For no reason whatsoever, I'm going to attempt some cryptography. (Is this the right section of the forum?) Here is a scenario, you are a hacker and your job is to spy on this other hacker. He is talking to a well known hacker. Here are his E-mails:

5:42PM (Suspects email)

Hey, so this INTEL is very important. You need to use that cypher the anonymous guy made. He didn't tell me much about the cypher, just that it was basic. I put in my message and this was the output: ò≡A≡Bk

The seed is '25565'

Can any of you guys crack this code? If you are having trouble, I can give you the answer. Is this a good cypher?

[MiiNiPaa]

Is this a good cypher?

No. Unless you can prove othewise. Reinventing the wheel in cryptography is as bad as trying to make a heart transplant without medical education at all: something will go terribly wrong.

[giblit]

Also whats up with the mod 256 instead of 26? But anyways it would be very hard to decipher considering you could have done numerous ciphers but more than likely a variant of rsa or shift.

I like this site though for cryptology. https://www.khanacademy.org/math/applied-math/cryptography

[RealGiganitris]

No. Unless you can prove othewise. Reinventing the wheel in cryptography is as bad as trying to make a heart transplant without medical education at all: something will go terribly wrong.

Just some fun. How could I prove otherwise?

(EDIT) Not either cypher, I will give you a hint: It uses the XOR operation.