eIDAS (Electronic Identification, Authentication, and Trust Services) is the EU regulation that establishes the legal framework for electronic signatures, seals, timestamps, and identification across all EU member states. It defines three tiers of electronic signature:
• Simple electronic signature (SES): any data attached to or logically associated with other data which the signer uses to sign — e.g. a typed name, a drawn signature, a click of accept.
• Advanced electronic signature (AES): uniquely linked to the signer, capable of identifying them, created under their sole control, and linked to the signed data such that any change is detectable.
• Qualified electronic signature (QES): an AES backed by a qualified certificate issued by a Trust Service Provider (TSP), with the same legal effect as a handwritten signature in every EU member state.
Most business contracts only require SES or AES; QES is reserved for cases where law mandates a handwritten-equivalent (real-estate transactions in some countries, certain financial agreements).