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One of the ways I quickly copy small texts from my computer to my Android phone is through a QR code generator. I pipe the clipboard text into my QR code generator on my computer, then I scan the QR code on my laptop screen using my android phone's camera, clicking a button to copy the text in android.

The problem is that the text may be sensitive. I can't do this for work passwords while in public places.

I notice there are QR scanning apps in the app store that are specifically marketed towards copying text into the phone's clipboard, but I'm struggling to find such apps that have any encryption. In other words, with the current options, copying/pasting via QR code will continue to involve potentially leaking clipboard data. I'd imagine this risk is mostly small. Who can memorize the layout of a QR code? The risk is highest in areas with CCTV. But in any case, if any small-moderate risk can be avoided, why not?

Does anyone know of a QR scanning app that uses public/private encryption/decryption keys? I.e. the app would produce a private key (which stays on the phone), and a public key (which goes to all the laptops/computers from which text is intended to be copied). The generated QR code would translate to gibberish if scanned by any device other than my phone (or any other phone with the private key). I know I could get this behavior by pasting the gibberish output into a second app that handles decryption (I'd imagine there are loads of those apps out there), but that inconvenience would negate the use of QR codes, and I'd probably revert to messaging/emailing myself with copy/paste data.

I don't want to use anything other than QR to do this, because I've had compatibility issues with the non-QR syncing apps for Android/PC.

I'm thinking of making an app like this myself someday, if it doesn't exist already, so I thought I'd ask first to save some trouble, or at least ensure I'm not reinventing the wheel.

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  • I don't see the requirement for usage of asymmetric cryptography here. If you have just one "source" (PC) and one "target" (Android phone) using a pre-shared symmetric (e.g. AES) key would have the same effect. If someone manages to get access to the key you are already in trouble.
    – Robert
    Nov 14, 2021 at 10:49
  • I suppose the ideal app would have options to use either symmetric encryption or public/private RSA. Symmetric would be somewhat useful for bidirectional clipboard transfer (using both the phone camera and laptop webcam depending on which direction). Usually though, I'd favor public/private keys, because there's a lot less to worry about regarding security: Only the security of the machine holding the private key is important (in this case, the phone). Plus you can easily share the public key without giving people the ability to decrypt. Nov 14, 2021 at 20:22

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