Signer Authentication

Signer authentication is the step where a platform confirms that the person signing a document is actually the person who was meant to sign it. It happens before or at the moment of signing, and the result becomes part of the document record. Without it you have a signature but no reliable way to tie it to a real human, which is exactly what matters if anyone later disputes the document.

Authentication runs on a spectrum from light to strong. The most common method is an email link: the document is sent to a specific address, and only someone with access to that inbox can open and sign it. A step up is a one-time passcode (OTP), where the signer enters a short code texted or emailed to them, proving they control that phone number or email at signing time. Stronger still is knowledge-based or ID verification, where the signer confirms personal details or uploads a government photo ID. Each level trades a little signer convenience for more certainty about identity.

Authentication feeds directly into attribution, the question of who did what. When a platform records that a signer opened a link sent to their email, entered an OTP, signed at a given time, and did so from a given IP address, all of that lands in the audit trail. That trail is what turns a click into evidence: it links the action to a verified channel and supports non-repudiation, the idea that a signer should not be able to credibly deny they signed. Under US Federal Rules of Evidence 901 and 902, this kind of corroborating detail is part of how an electronic record can be authenticated for court.

How much authentication you need depends on the document and the law that applies. A US contract under the ESIGN Act (2000) or UETA (1999) generally requires intent to sign and association with the record, not a specific identity method, so an email-based simple electronic signature is often enough for everyday agreements. UETA has been adopted in 49 states plus the District of Columbia; New York instead relies on its own Electronic Signatures and Records Act (ESRA). Higher-stakes or regulated documents call for more. Under eIDAS (Regulation (EU) No 910/2014), an advanced electronic signature must be uniquely linked to the signer and capable of identifying them, and a qualified electronic signature goes further, based on a qualified certificate issued by a qualified trust service provider. Choosing an authentication method is really choosing how strong you need the identity evidence to be.

Examples

• A signer receives a sign.pink link at their work email, opens it, and signs; the platform records that only that mailbox could access the document.
• Before signing a higher-value agreement, the signer enters a one-time code sent by text, proving they control that phone number at the moment of signing.
• An audit trail shows the signer's email, the time they verified an OTP, and their IP address, all tying the signature to a verified channel.