I need to crack a stream cipher with a repeating key.
The length of the key is definitely 16. Each key can be any of the characters numbered 32-126 in ASCII.
The algorithm goes like this:
Let's say you have a plain text:
"Welcome to Q&A for people studying math at any level and professionals in related fields."
Let's say that the password is:
Then, to encrypt the plaintext, just XOR them together. If the key isn't long enough, just repeat it. e.g.,
Welcome to Q&A for people studying math at any level and professionals in related fields.
I have 2 English messages encrypted with the above algorithm and with the same key. I know about the communicative property of xor and that it can be exploited for the example above. I've read that this is a pretty weak cipher and it has been cracked. However, I have no idea how to do it. So, where can I find a cryptanalysis tool to do it for me?