In my previously-posted Work Backup program, the script copies changed files to another location. One use is for "backup buddies" on a network (or with DSL etc.), so I'm adding features to make the files encrypted. I've got that part well in hand.

However, what about the file name? I'd like that to be safe from prying eyes (even accidently), too.

Now I could maintain a dictionary and simply assign meaningless names like file123456.dat to the destination. But I want to do without a central list, and make each file individually 1:1 reversable. That is, encrypt the file name and be able to decrypt it.

But, a regular encrypt will produce byte values that are in a larger range than the input. File names may be 94 ASCII characters, for example, but the output will be 0..255 fairly uniformly. That won't work for a filename!

A simple idea is to then BASE64 encode the results. That should not increase the length =too= badly. But I wonder if there may be a more elegant way, such as encrypting using a stream cypher that maps 94 input chars to the same 94 output chars. Does anybody know of such a thing?

—John

In reply to Encrypting a Filename by John M. Dlugosz

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