In Warlords it is common in the belt and asteroid colonies to "hand out" barcodes to individuals for security and labor reasons. With a simple scan the station security or guild master can see the basic bio of this person, past work and incidents, which ship they came on, etc. They are deemed more humane than chips and only slightly invasive by society at large, but are only prevalent in the outer colonies.

I would need (in my mind) these bar codes to be able to remain the same physically, but the information accessed can be changed over time. As well as having some sort of machine doing the tattoo to confront forgeries.

Is it worth the effort to tattoo thousands of miners and ship crews or would something else be far more efficient? Also would the idea of tattoo barcodes even work?

  • $\begingroup$ you could have the tattoo as a bio-chip that when you get a job the employer scans you and the tattoo would then update your info (would just be easier to just use normal chips instead) "only slightly invasive then chips" well some people are using chips today and its far more hidden then a big tattoo. not to mention it's ripe for abuse just rip the skin off a miner spray on skin and bam your inside a rival mining rig $\endgroup$ Commented Jul 31, 2018 at 4:09
  • $\begingroup$ @Creed Arcon I feel that a chip would be easier to hack (if you could hack it) then tampering with a tattoo. Also you can cover up a tattoo a chip would always be active . $\endgroup$ Commented Jul 31, 2018 at 4:11
  • $\begingroup$ you could use both, the chip as a scan when they are at checkpoints, then if the guard is not convinced the bio locked tattoo (means only your DNA that makes the tat work). hold out your arm citizen beep its not john doe kill him. but if it just a normal tattoo i don't think is worth it $\endgroup$ Commented Jul 31, 2018 at 4:16
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    $\begingroup$ Is this for identification or authentication? Because a barcode is trivial to copy, so if you can use it to open a locked door, it's a really bad idea. $\endgroup$
    – Erik
    Commented Jul 31, 2018 at 5:08
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    $\begingroup$ Barcodes were invented when reading DNA was sci-fi. It is like a horse carriage. Why would anyone with future space technology use it? Read the DNA with a laser. Or quantum radar. Or read brain patterns. $\endgroup$ Commented Jul 31, 2018 at 10:19

8 Answers 8


They are deemed more humane than chips

Do you know why the Nazis tattooed serial numbers into the arms of concentration camp prisoners? Because it marks them for life as something they deemed inferior, worthless, the enemy, outsiders. It is definitely not humane to mark someone as a laborer and cut them off from any chance to ever climb the social ladder.

If these barcodes are only used in the belt and asteroid colonies, tattooed people will probably face discrimination just because they wear a visible mark that distinguishes them from residents of planets and other colonies. Compare it to todays racism, where people are judged and discriminated because they have dark skin, slitted eyes or some other visible feature that has nothing to do with their personality or worth as a person.

Additional disadvantage: It's rather easy to exploit, alter and otherwise temper with tattoos. You can cut (parts of) the skin off, thicken barcode lines with your own tattoo machine or use laser removal methods. All you need for identity theft is a high resolution photograph of someone else's tattoo.

If you want something unique and identifying, choose a fingerprint or a truly quick DNA test or implant some chip into a bone of an infant. A DNA test has to be coupled with a second identifier because identical twins have basically identical DNA.

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    $\begingroup$ "identical twins have identical finger prints." Identical twins don't have identical fingerprints. +1 though for the first paragraph - wish I could upvote multiple times just for that. $\endgroup$ Commented Jul 31, 2018 at 6:16
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    $\begingroup$ I wouldn't be the least bit surprised if the German government of the 1930s and 1940s would have used subdermal contactless chips if those had been available. (Remember that various groups were also required to wear other visible markings.) Alas, they weren't, so they used what was available and suitable for the purpose. (One can and probably should argue that the purpose was wrong, but if one believes that the purpose is good, then it comes down to solving the problem, and tattoos did solve the problem.) $\endgroup$
    – user
    Commented Jul 31, 2018 at 6:30
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    $\begingroup$ "If you want something unique and identifying, choose a fingerprint" *almost unique. On the scale of thousands of workers that would still work well, but if you scale it up to billions or trillions then it might not hold up so well. en.wikipedia.org/wiki/Fingerprint#Errors $\endgroup$ Commented Jul 31, 2018 at 15:52
  • $\begingroup$ How did those prisoners live in the society after having liberated? $\endgroup$
    – Ooker
    Commented Jul 31, 2018 at 16:04
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    $\begingroup$ Initial argument in this reasoning is unrelated to the question. The people in the outer colonies of the story have decided they like barcodes better than chips. Also the OP makes no mention of the fact that these barcodes carry some kind of unavoidable stigma with them. Just because you beleive the process of putting a barcode on the skin is inhumane, does not mean the people in the story the OP described feel the same. Aslo, the context matters, this is a job, not prison. -1 EDIT: to Add, if people can live in the outer colonies in a sci fi setting, tattoo removal likely wont be an issue. $\endgroup$
    – VampyreSix
    Commented Jul 31, 2018 at 20:48

What you describe is a database with the entry key being the tattooed bar-code.

The main problem I see is that to scan an individual you would need to access open skin, which in space is generally cumbersome when one is wearing a space suit: imagine having to scan miners accessing the mine, they are already fully dressed, to uncover part of their body would require additional time which would be subtracted to operation.

It sounds much more practical to scan the iris and use it as access key.

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    $\begingroup$ I was thinking the barcodes would be used on board the ship, air locks right before entry, and space stations. Maybe their suits also have custone barcodes that work kinda like dog tags? $\endgroup$ Commented Jul 31, 2018 at 4:04
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    $\begingroup$ @CelestialDragonEmperor, swapping a suit is really easy. $\endgroup$
    – L.Dutch
    Commented Jul 31, 2018 at 4:46
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    $\begingroup$ @Cadence, that adds additional complexity to the system. OP is looking for practicality. $\endgroup$
    – L.Dutch
    Commented Jul 31, 2018 at 5:22
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    $\begingroup$ "swapping a [space] suit is really easy" I recall reading on Space Exploration, but am not up to digging out that Q&A at the moment, that present-day space suits are individually tailored. With ordinary clothing, something being off by a few cm is no big deal; with a spacesuit, it can be crippling. $\endgroup$
    – user
    Commented Jul 31, 2018 at 6:27
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    $\begingroup$ You can simply add a small piece of plexiglass or similar to the suit where the code is located, can scan through it. Or just use highly metallic / radioactive ink so it can be scanned with something that doesn't need visuals - possibilities are endless if you just want to $\endgroup$
    – dot_Sp0T
    Commented Jul 31, 2018 at 7:38

Tattoos are not more humane and less invasive than chips, depending on how each thing is used. Tattoos will be very visible on you, specially if they have to be somewhere easily accessible for scanning. They can also trigger allergic reactions which will be a permanent hassle to whomever you've inked until you can get them surgically removed.

Chips are less likely to trigger allergies. They can be smaller than a grain of rice today, so they might be microscopic when we become a spacefaring civilization. They are not visible and will not take space that you could use to tattoo something else. If all the chip does is give out a constant string of bits - which is all you need to access a database - it will outdo tattoos regarding how invasive and how efficient it is.

A chip will also be much harder to tamper with - with a tattoo, all you need is some ink and a needle to make a machine think that Peasant Joe is Mr. Tycoon McRichie. With chips, you need the services of a very expensive hacker.

In the end, biometry beats both. In China you can pay for a meal by smiling at a camera. This is deemed more secure nowadays than using a credit card with a chip. Credit card chips can be cloned with equipment that is reasonably cheap in some black markets (compared with the costs of making or modifying tattoos), but in order to cheat real time movement-tracking facial recognition you need a series of facelifts to look like your mark, and that takes a serious amount of time, money and detachment from your own image. Add a IR layer and not even that will do - even identical twins don't have the same thermal features. And all the equipment you need is a slightly more sophisticated version of a 21st century Kinect or Playstation 4 camera.

Go with biometry. You can't go wrong with it.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Monty Wild
    Commented Aug 1, 2018 at 20:22

One very important aspect to consider: Information security.

When you tattoo a person for easy scanning, you are putting a machine readable number on them. Anyone can read that number and replicate it as a sticker to impersonate that person. This would work even at a distance, it suffices that the entire tattoo becomes visible to the attacker once.

Any biometric marker performs much better than a tattoo in this regard: The biometric marker generally can not be measured at a distance, and is generally much harder to fake without being obvious. Nevertheless, biometric markers can generally be spoofed in the same way as a tattoo. Think for example finger prints: Any person leaves their fingerprints everywhere, so it's easy for an attacker to covertly obtain the whole set of their targets fingerprints. After that it's a simple matter of creating a silicon cover for their own finger to fool any fingerprint sensor.

So, if you want real security, you must use chips. The difference is that a chip is an active component; it can perform cryptographic computations by itself. This allows the chip to

  • Tell the scanner its identity, and to

  • actually prove to the scanner that it's really that chip,

  • without disclosing the secret key that's used for that proof.

If the chip is built well, it cannot be copied without really, really expensive equipment, destroying the original in the process. As such, the greatest danger of using chips is, that someone's chip is taken away by force to be used by the attacker. Think: Kill the guards, cut out their chips, and enter whatever they were guarding. Impersonation is not impossible, but it becomes damn hard to cover up.

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    $\begingroup$ it would also be fairly easy for a person to change their tattoo and therfore disappear from the system $\endgroup$
    – jk.
    Commented Jul 31, 2018 at 19:34

In the world of pets both tattoos and chips are already widely used as a means of marking animals so that if it is somehow lost to the owner it can be recognised and brought back.

Just to make it very clear - whatever method is used it contains merely an identifier that is linked to a database entries. Any solution where the agent (tattoo or chip) should contain also the data requiring updates is prone to too many errors and problems.

As far as I can see the general direction is to use chips rather than tattoos. And there are few good reasons for that:

  1. Implanting a chip is far easier, less invasive and time consuming than putting a tattoo. I guess everyone knows these days how much trouble it is to make even a simple tattoo. Implanting a chip is a single simple injection with a chip itself being a bit larger than a single rice grain. Also making a tattoo is rather painful. Again, implantation is simply an injection.
  2. The chip lasts longer. Since it is using an RFID technology it does not require any power (the power is induced from a scanner to send back a signal). There is hardly anything that can break or fail. If it works it'll work for years and years. And it will always produce the same return signal. The tattoo is exposed to all the risk the skin is. It fades over time, gets blurry as the ink dissolves to some level, might become unreadable due to scars, burns etc. As a result it might even produce a different value than it had initially. Of course you might do a correction to a tattoo or even make a new one if the old is entirely unreadable but that brings us back to point one ;-)
  3. Skin imperfections might make it difficult to effectively place a tattoo in a specific skin location. If you have a scar you can cover it with a tattoo of course but it won't be a precise one with sharp lines (as needed for bar codes). Similarly mole might cause it impossible to blacken a specific spot. I believe you should try using the same place for the identification tattoos to avoid multiple identities of a single person. A chip might be prone to similar problems (sometimes - but rarely it can actually even shift its position) but it's far easier to scan entire body with a proper scanner than to scan entire skin.
  4. Chip resides under a skin, thus is invisible so it's less obvious. Of course it can work both as a benefit and a drawback depending on the goal to be achieved. But still if we're considering more humane option, I would consider something invisible better here.

Note, I'm not referring to artificial identification versus biometrics here as that is not what the OP has asked for. I'm also referring to the currently existing technology.

And guess what, not only the technology is in place, it has also already been enabled to people who wants to use it and are lucky enough (?) to have it within their range. Some reading to find out more.

BTW, all my pets have chips implanted ;-)


If you're in a space-scenario, there's a good chance people have chips anyway - after all, it's the most reliably way to enable interfaces which react on your thoughts.

Depending on the situation, a barcode is heavily unreliable. Its main problem is that a barcode merely represents a bit of data - it's basically a number in a format that is easy to read for machines.
And just like any other data, you can copy it. Increasing the amount of data (i.e. making the tattoo more complex) is a failed idea as well. You can't just arbitrarily increase complexity, or else the tattoo will change over time.

So, a barcode alone isn't all that useful. Combining it with retina scans or the like doesn't make sense either, as the barcode would be the weakest link, and therefore be negligible.

If you still want to pull through with this idea, I would advise to make the ink nanobots: The tattoo would become a computer, capable of cryptographically save interaction, but also have a failback-mechanism for cases when no higher technology is available (or needed).

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    $\begingroup$ I like this answer. I should add that it's quite a common concept in fiction to have interactive/context-sensitive tattoos. Examples include the magic ones in harry potter used by the Death Eaters, I remember many other examples, but can't name them off the top of my head. Generally the theme is that you can make them visible or hide them either at will or by pressing on them. Smart Tattoos are actually already something being developed as well. Harvard are making a smart-tattoo to monitor the blood-sugar of Diabetics for example. $\endgroup$
    – Ruadhan
    Commented Jul 31, 2018 at 11:03

Tattoos might be ideal:

  • They need not be completely legible visually, making them hard to copy without the wearers consent. Checksums or additional information may be incorporated in magnetic features of the ink (easily checkable by contact, impossible even at a slight distance), chemical composition of the ink may hold information and is esily checkable by Raman laser spectroscopy, inks of different colors can be set in close proximity, so only microscopic inspection will reveal there is more than one (mix) color. Multiple tattoos have to be pointed out by the wearer to make sense of more private information. By making the application process more technical, the bar is higher for the inevitable forgers.

  • They are on the outside, making them much easier to be checked for manipulations. Anything implanted will communicate on radio or light frequencies without the communication partner in direct contact - this is ideal for man-in-the-middle attacks or spoofing by having powerful hardware in the background that can outcompute the partner. Touch-only reading of a tattoo with additional security features ensures that the read person will be aware of the reading, and the reader will be sure that the thing she is trying to read is actually the one doing the talking.

  • They can transport a tidy amount of information. Think QR-codes.This would come in handy in scenarios where databases are prone to error, forgery and viruses. The tattoo is the document, not just a database key. The data may also be centrally stored somewhere, but the primary document is right there. Just like paper money can be forged today, this will inevitably lead to some people polishing their CV by adding entries, but if the positioning of the tattoo is also information, this will be very tricky ("So, Mr. Anderson, you are saying that between your stint in McDo in 2456 (elbow) and your present application in 2458 (lower biceps) you served in the Space Force, were VP of PR at PwC and built a company, all the while suffering a burn on that prison shaped spot on your forehead?"). Blockchain! (well ok, that's not how that works... but it's a chain of sorts!) Detected forgeries are highlighted, and a forger-spot (one unlikely to suffer large scale damage, like the white of the eyes) is populated with the details of the crime.

  • They can be made very resistant to theft. While the close-proximity stipulations are all well and good for the normal minded forgers, more bloody minded criminals may be open to removing interesting tattoos wholesale, for later analysis. While this largely the same predicament that chip-wearers face, some of the same precautions can be taken: Materials that are dependent on good oxygenation (now the robbers need a medreactor to put the skin in), Steganography (which of these is his Club-card?), and others.


Since you're mining asteroids, I'm assuming we're talking a society that's at least 100 years ahead of us. In that case, bar codes are fairly pointless.

Facial recognition today is good enough to work for many consumer grade applications. In 100+ years, it will be flawless. And there certainly will be better biometric methods that come along. Perhaps instant, remote DNA analysis. Bar codes on people in this situation bring very little to the table.

Bar codes might still be useful for tracking equipment, but they will be a decidedly old school method of doing so.

  • $\begingroup$ facial recognition is the direction, in the future maybe body / iris / brainwave scan? or else: tattoo and barcodes and any method used to mark somebody is just non practical anymore (tg) $\endgroup$
    – Edoardo
    Commented Aug 1, 2018 at 15:41

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