A good ID scheme can preserve privacy when it includes functions to do anonymous attestation. For instance if you are required to prove age or residence, but th

A good ID scheme can preserve privacy when it includes functions to do anonymous attestation. For instance if you are required to prove age or residence, but the other party does not need any other information about you. A scheme which supports hashed identity (e.g. hashing your ID number along with the ID number of the party requesting, resulting in a unique identifier) can be used for services that require one account pr. person. When this is available out-of-band (e.g. a smart card or app [not requiring going through government servers each time]) no leaks can occur.