Signieren

Signieren is the act of affixing a signature to a document to indicate consent, authorization, or verification. Signatures can be applied in a physical form with handwriting or in electronic form using digital tools. The method chosen affects how authenticity and integrity are established and how the signature is verified later.

Forms and standards: Handwritten signatures on paper remain common for many agreements and official documents. Electronic signatures cover a spectrum from simple scanned marks to cryptographically secure digital signatures. Under the European Union eIDAS regulation, electronic signatures are categorized as basic electronic signatures, advanced electronic signatures (AdES), and qualified electronic signatures (QES). A QES, created with a qualified signature creation device and a qualified certificate, has the strongest evidentiary value and is generally treated the same as a handwritten signature in law. National laws, such as Germany's Signaturgesetz (SigG) and related regulations, implement and harmonize these rules at the national level.

Technology and practice: Digital signatures rely on public-key cryptography. The signer uses a private key to produce a signature on a document's hash, and others use the corresponding public key to verify it. Trust is anchored in digital certificates issued by trusted certification authorities, within a public key infrastructure. Processes may include timestamping, certificate revocation checks, and secure key storage to prevent forgery or key leakage.

Practical considerations: Signatures serve purposes of authentication, integrity, and non-repudiation. They are often required for contracts, official filings, and regulatory compliance. Verification involves checking the signature’s validity, certificate status, and the integrity of the signed content. In professional workflows, sign-off can also denote approval of documents or changes, sometimes through workflow systems or electronic signing platforms.