Pseudonym

A stand-in name that keeps you accountable but not exposed: how eIDAS protects pseudonyms in wallets, logins and qualified certificates.

An identifier that stands in for a person's real name, without the person becoming anonymous: somebody, usually the issuer, can still establish who is behind it.

eIDAS protects the use of pseudonyms in three places. Article 5 says the use of pseudonyms chosen by the user shall not be prohibited, without prejudice to rules of Union or national law that require identification or that give pseudonyms a particular legal effect. Article 5a(4) requires an EUDI Wallet to be able to generate pseudonyms and to store them encrypted and locally in the wallet. And Article 5b(9) tells relying parties that they shall not refuse the use of pseudonyms where identification of the user is not required by law.

In signing, a pseudonym can appear in a qualified certificate instead of a name, and the rules for validating a signature require that the use of a pseudonym is clearly indicated to the relying party - so a counterparty knows it is dealing with a verified person under a pseudonym rather than with an unverified name. That combination is the point: identity verification happens once, at the QTSP or the wallet provider, and after that a service only learns what it actually needs. A wallet that issues a different pseudonym per relying party also prevents those services from recognising the same person across sites, which is the practical half of unlinkability.