# What does a repeated byte between two XORed hexadecimal ciphers mean?

I have two different hexadecimal strings (of same length) that I think are encoded plain text strings.

Out of curiosity I XORed them and I found a single hex byte repeated for the length of the two hex strings.

Does it mean anything about the key or the algorithm used to encode the two original strings?

EDIT:

Here is an example:

• String1: 12345678
• String2: b294f6d8
• XOR: a0a0a0a0

And I think I may know part of the plain text.

• Do you know anything about the plaintext? Mar 5 '20 at 1:43
• Maybe a padding block and that the repeated byte is the amount of padding (PKCS#5)? Mar 5 '20 at 7:30
• Sure, it is likely that the XOR value you're seeing was used on string 1 (the one that makes most sense) to obfuscate it, giving you string 2. I call it obfuscation because a repeated single byte key is so easy to crack we cannot call it encryption. Mar 5 '20 at 15:24
• @MaartenBodewes, it was just a quick and dirty example, those are not the real keys and in my case string1 and string2 are both encrypted keys/hashes/whatever. Mar 5 '20 at 16:40
• Well, for a reused key in a XOR cipher you can simply tell that $c_1 \oplus c_2 = p_1 \oplus p_2$ but that should not be news to anybody who studied a bit about one-time-pads. If they are both ciphers over the same plaintext then the key has changed two bits instead. Mar 5 '20 at 16:45