What is a reliable source (verlässliche Quelle), and what is an authentic source?

A reliable source is any information source considered trustworthy for a concrete situation, such as a register or a deed; an authentic source (eIDAS 2024/1183) is a repository or system run by a public or private body that holds attributes about a person or object and counts as the primary source for them or is recognised as authentic by law.

eIDAS 2015/1502 defines a reliable source as any source that reliably provides accurate data, information or evidence usable for proof of identity.

Go deeper:

• Implementing Regulation (EU) 2015/1502 (EUR-Lex) — defines the authoritative source and the assurance levels low, substantial and high.
• Regulation (EU) 2024/1183 (EUR-Lex) — eIDAS 2.0: authentic sources and the European Digital Identity Wallet in law.