This can at most buy you a constant factor - useful, but not very. ... Someone else on this list mentioned that an edge detection algorithm ... It could give you a quick go/no go.
Don't forget that in most cases it'll be obvious that it's the wrong key - only when it isn't would you submit the thing to a second-level analyzer to check for edges/characters etc.
I'm confused here. How will it be obvious? Unless you mean that you're going to sit there and watch it while it goes through the, (on average), 999999999/2 keys it would have to try before finding it. That could take awhile and really slow things down if it took user intervention for each test. You can't beat the human eye on visual discrimination though. Patrick _______________________________________________________________________ / These opinions are mine, and not Verity's (except by coincidence;). \ | (\ | | Patrick J. Horgan Verity Inc. \\ Have | | patrick@verity.com 1550 Plymouth Street \\ _ Sword | | Phone : (415)960-7600 Mountain View \\/ Will | | FAX : (415)960-7750 California 94303 _/\\ Travel | \___________________________________________________________\)__________/