From part of a cryptanalysis tool I was writing, the other day.
A way of obtaining possible XOR'ed string values.
If you ever get to the point in the analysis that you can simply XOR the string to get closer towards your goal, of finding a weakness, this might be what you need for the job.
Assuming that the value that was XOR'ed was an ASCII value 32-254(typical range),
all we have to do is loop about XOR'ing, and checking if it's in that range.
Of course.... there's still probably more work to do; even, after you create a list of possible XOR values, but it's a step closer.
Note: Small input such as, "stuff", will create over a hundred possible values, but input such as, "Stuff.", will generate a nice concise list.
Hope this helps you in analyzing, and strengthening your next encryption algorithm.