Advanced Electronic Signature (AES)

Advanced Electronic Signature (AES) is the middle of the three signature tiers defined by eIDAS, the European Union's electronic identification and trust services regulation, Regulation (EU) No 910/2014. It sits above a Simple Electronic Signature (SES) and below a Qualified Electronic Signature (QES). The purpose of the AES tier is to raise the bar on trust: instead of only capturing intent to sign, an AES ties the signature firmly to one specific person and makes tampering detectable after the fact.

eIDAS sets four requirements for a signature to count as advanced. It must be uniquely linked to the signer; it must be capable of identifying the signer; it must be created using electronic signature creation data that the signer can use, with a high level of confidence, under their sole control; and it must be linked to the signed data in such a way that any later change to that data is detectable. In practice, those last two points usually mean a signature backed by cryptographic keys, where the signed document is sealed so any edit breaks the seal.

Two ideas do most of the work here. Uniquely linked means the signature can be traced back to one individual, not a shared inbox or a generic credential. Tamper-detectable means the document and its signature are bound together, so if a single character changes after signing, verification fails and the change shows up. This is what makes an AES stronger evidence than a basic checkbox or typed name, and it is closely related to how a digital signature uses keys to protect a document.

AES is a legal category, not a single product, so different providers meet the bar in different ways. It is most relevant when you sign with parties in the EU or under eIDAS, since the SES, AES, and QES tiers are an EU concept. In the United States the governing laws are the ESIGN Act (2000) and UETA (1999), which do not use these tiers; they treat a valid electronic signature as enforceable without grading it. sign.pink seals every document with a tamper-evident audit trail so changes are detectable, which is the core protection the AES tier is built around.

Examples

• A signer in Germany approves a supplier contract using a key-backed signature that ties the document to them and breaks if the file is later edited.
• An EU bank requires AES rather than a basic typed signature for a loan agreement, so the signer's identity and the document's integrity can both be verified.
• After signing, someone alters one number in the contract PDF; the signature no longer validates, exposing the change.
• A cross-border deal between an EU and a US company chooses AES to meet the European party's eIDAS expectations.