View Full Version : D20 Modern Question - Fingerprinting Technology

February 21st, 2009, 02:39
Good Day Everybody,

Unless in some ways I could have missed this information, then call me blind for asking this in this forum hoping of course that nowhere else this has ever been asked.

In the campaign I am putting together, my players may have to defeat fingerprinting technology and although difficult it should be, I'm wondering the kind of DC this would have. The logic of the number is also important so that I can use the answer for future reference.

Thanks in advance for the information, everybody here have been a bag of wisdom so dearly needed sometime,



February 21st, 2009, 06:00
I wrote a fairly long post about this but erased it because I realize a lot of what I was saying boiled down to something much mroe simple: A DC for me is really all about how much of a reward I believe the task is. I haven't played d20 modern in a long time (and when I did, it wasn't for long) but I did play many years of d20 so I feel qualified to say that DCs in d20 should be relative to reward, with a +/- 2/5 for realism. Realism is nice but the driving factor in a game should be reward. If you disagree, feel free to ignore this advice, obviously.

In DnD, characters are generally rewarded in gold, or in things that could be purchased in gold. There are exceptions to this rule but generally even if a character can't buy something, like information, they could still put a price tag on it after-the-fact, so every reward has some numerical value, even if it's a vague one. I believe its much the same in d20 modern (indeed, in any game).

Set the DC based on the reward. An easy DC should not provide access to high (or even medium) rewards.

Incase it hasn't become clear by now, I strongly believe that DCs that have no reward and only progress the story are generally pretty useless (which, by the way, is why I love skill challanges in 4e). If your fingerprint lock needs to be bypassed to advance the story then it doesn't matter what the DC is, they'll eventually break it. The higher you set it, the faster you bore your players (in my opinion, anyway... you know your players better than I do).

If, however, your fingerprint lock has a reward, place a monetary value on it. Just guess. Let's say the fingerprint look allows the group to surprise a potential target. That makes the encounter easier to some degree. Try to how much the characters would pay, in cash, to have this fingerprint lock bypassed. That's the reward. Set the DC accordingly.

Now, I still haven't answered your question because I haven't provided you with a number. Well, if you agree with me so far, the rest is easy. Assuming a basic (easy) reward should have an average DC, an average character should be able to defeat it with a roll of ten. Meaning a character with no bonuses from training/specialization, only standard bonuses from level (though I don't believe these are present in d20). I would say a good baseline for medium rewards is a roll of fifteen, and a roll of twenty for hard rewards. Of course, characters with training and specialization will have an edge on these rolls and that's kind of the point of specializing.

So you need to answer, what's the value of the finger-print lock? What's it worth in monetary terms? Based on that, start at 10 and work your way up.

As a last note, one final way to adjust your DC is to consider what you want their chances of success to be, then take the best PC's bonus to the applicable roll and figure out the DC from there. If you want 50% and the best PC's applicable skill bonus is a +10, the DC should be about 20.

Let me know if this isn't what you were looking for of if I was unclear and I will try to clarify. Good luck!

Ram Tyr
February 22nd, 2009, 22:58
Just because it is related...you may not have heard that a report mandated by Congress in the US about two years ago was recently issued and shed a lot of light on the 'strength' of the various forensic techniques the public has become convinced are foolproof. (Remember, this was a scientific critique.)

Just one article...

So, that goes to the question of how 'difficult' it should actually be. However, you might allow some of the investigative skills to be used and then the social skills to try to win the lead investigator, the prosecutor, the jury... over to being critical to the technique used. This is clearly, not exactly what you are asking about, but some people really enjoy using this kind of 'current event' in their modern campaigns. Since it matches up so nicely with your question, I thought I would toss it out there.

Oh, and sorry if this interferes with anyone's enjoyment of those law enforcement forensic television programs. Just continue suspending your disbelief!


February 23rd, 2009, 05:30
Fingerprint readers are ... far less safe than people would have us believe. The cheaper ones can easily be defeated by a rubberglove or even a superglue layer. ( I even saw an example using a scan of someone's fingerprint used on a more expensive device, pressing their thumb over the paper with the readout.) So the difficulty might be ... far less than expected.

Even villains might fall for hype after all.

- Obe

February 23rd, 2009, 08:56
*Snicker* Obi, the cheap ones can be defeated by just a file swap. I was working on my master’s a year or so ago, killing time in the computer lab, waiting for a class to begin in a few hours. Another grad student came in that I knew. He had just bought a cheap thumb reader on a close out sale for like 5 bucks.

It said in huge letters on the package the thumb reader was not to be used for security purposes. The lab TA, myself, and the other guy all speculated on why. Literally 10 minutes later we had the hardware installed and had scanned two thumbs and swapped the thumb print data so the thumb reader thought the two thumb scans were each from the other guy. There was zero protection on the thumb print files.

Both for reality and for game purposes in some cases it can be very easy to manipulate digital data, even where the data is actually being protected. In a game the level of protection would determine the DCs to hack that type of data.

February 23rd, 2009, 10:10
Mhm... So a DC of 5 for Computers?
.... or a DC of 35 for a sledgehammer? ;)

- Obe

February 23rd, 2009, 19:35
I think you are being generous with the sledge. ;)

February 23rd, 2009, 21:55
Nonono... The real problem is finding the right person to apply the sledge to. Heck find the VERY right person (preferably a cowardly computer tech) and the DC might be as low as one. :)

- Obe

February 24th, 2009, 13:24
If you had my players they'd save you the trouble of coming up with a DC by going and chopping off the fingers of someone who has access.....:D