decrypting aid

Hi all,

I'm trying to decipher a system which communicates in short bursts of
about 100 bytes encrypted data. I know a subset of 6-10 bytes in each
of those 100 bytes, but the rest is unknown.

Are there any software tools out there that analyze the encrypted data
and would permit to make educated guesses on what kind of crypto system
is being used? Anything that might actually help with finding keys that
were used for XOR'ing data? I have reason to believe that a really
simple method (such as XOR'ing) is being used.

Thanks

- Balt

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