Getting Fingerprint Readers to Read Your Prints?

crypticgeek asks: "I recently obtained a new job, and I'm already at my wit's end. Many of the doors in our facility have finger print readers because they are high security areas. No matter how hard I've tried, I can't get the system to read my prints very well, since they aren't well 'defined'. This means I don't have access to the areas I need to. I have to have someone else let me in to secure areas. I've tried using lotion thinking they were too dry, but that didn't work. In fact, most of the time my hands are really sweaty. Someone suggested I use nail polish remover and that would 'raise' the print, however I'm skeptical. Has anyone else had problems with finger print devices, or know of some possible ways of getting a better read?"

Comments

In the old days

[2.7182]

The FBI has a special recommended way to clean hands before getting prints. You washed your hands in soap, then rinsed in alcohol, and then air dryed, no towel.

This is a problem. Here are some ideas.

[swillden]

I've been doing biometrics related stuff for the last several years, and I can tell you that there are a *lot* of people who don't have easily-scannable fingerprints. Many people who do a lot of work with their hands basically keep their fingertips polished smooth. One colleague of mine has a grandmother who quilts a lot and the constant rubbing of fingertips against cloth erases her ridges. A national ID project in Nicaragua (IIRC) ran into lots of trouble because most of the women cook tortillas and frequently grab the hot tortillas with their fingers to flip and remove them, burning their fingerprints off in the process. People who do hard labor often have thick, cracking callouses which cause problems.

It also appears to be a bigger problem for women than for men, women seem to have naturally fainter ridges than men, and asians seem to have fainter ridges that other races. I've met lots of asian women who have basically no ridges at all.

Other people have a different problem. Most fingerprint recognition algorithms want to look at some nice whorl patterns, which is where the most identifiable splits and changes in the ridges are found, but this "central" portion is not very centered on some peoples' fingers. For some, it's closer to the fingertip or closer to the knuckle, and I even met one man who got the best readings by tilting his finger about 30 degrees to one side.

Finally lots of people have problems using fingerprint scanners because they don't know how to use them. "What's to know?" you might think. Actually, you do have to learn how to position your finger on the sensor, and how much pressure to apply. Bad positioning, or too much or too little force, will give you poor scans.

So, to find a solution (other than getting your employer to fix or get rid of the scanners), I suggest you firse see if you can figure out what the problem is. Some things to look at/try:

1. Play with positioning. If there's a scanner somewhere that actually shows you the image it scanned, play with that. Look at your finger and figure out where the most "interesting" part is and try to get that centerd on the scanner. Figure out how much pressure to apply so that you get nice, clear ridges that are distinct and well-separated.
2. Make sure the template is good. When you scan your fingerprint, the scan has to be compared against a template that is stored somewhere. Maybe you didn't get a very good scan when the template was created? Usually, enrollment systems scan your finger multiple times and either combine the results or take the one they estimate to be the "best", but it may be that you still didn't get a good template. Try re-enrolling after you've figured out the ideal way to position your finger.
3. Think about what you do with your fingers. If your ridges are just very light, perhaps they're not naturally that way. Is there some activity you engage in that wears them off? If so, you might consider stopping that activity. On the other hand, if it's something you do so much that it polishes your fingertips, it's probably something you really like doing (or something you do obsessively...).
4. Experiment with moisture. It sounds like you're already doing this, but try a few different things.
5. Consider making a fake finger. If worse comes to worst, it's supposed to be pretty easy to make fake fingerprints, and there are recipes on the web. I've never done it but I've seen it done, and it looks easy. Making a fake will allow you to do whatever it takes to get one really good print from your finger, and then you can just use that. If you need to, maybe you can even use someone else's fingerprint ;-). The security folks may not like this approach, of course, but you can always try pointing out (after you've learned how to do it) that if it's so easy, then their security technology isn't much good anyway.