The digital wallet could be something like an Yubikey that holds the data and decryption software. The stipulation that it should be available to everyone is th

The digital wallet could be something like an Yubikey that holds the data and decryption software. The stipulation that it should be available to everyone is that it needs to be readable from a mobile phone (eg NFC). The phone would issue a request for access to some policy, and the device would read the data and issue a true/false response (or more if necessary.) The wallet holder would have control over what their wallet gives the reader access to. I imagine a mobile app would be cheaper and simpler though.