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Are there any practical limitations? Govt driving license, passport, SSN could be digitally signed making it easy for anyone to validate. They can have a qr code in them which can be easily validated using an android or ios app offline if the corresponding public key is pre installed. This will make fake ids impossible. Why is it not done even in developed countries like united states?

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closed as off-topic by fkraiem, cpast, DrLecter, Seth, cygnusv May 27 '15 at 8:09

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions about security policies that may be based on cryptography (as opposed to the design of cryptographic algorithms and protocols) are off-topic here, but may be asked on Security." – fkraiem, cpast, DrLecter, Seth, cygnusv
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ I voted to close as off-topic since this is about security policies, not cryptography per se. You should ask this on Security.SE. $\endgroup$ – fkraiem May 27 '15 at 2:34
  • $\begingroup$ A QR code is easily copied. Putting a digital signature on a QR code on each ID won't prevent making a copy of a valid ID. It won't even prevent changing the photo on the copy, unless the photo is available from an online database (and if we have this, we hardly need the signature in the QR code). $\endgroup$ – fgrieu May 27 '15 at 15:27
  • $\begingroup$ @fgrieu Agree photo can be changed in smaller ids. Encrypting/encoding photo will require a huge qr code. may be possible with passport. At least other details can be validated offline $\endgroup$ – balki May 28 '15 at 4:30
  • $\begingroup$ @fkraiem can you please move the question to Security.SE? $\endgroup$ – balki May 28 '15 at 4:31