What a Signature Does

In one line

A signature does four jobs, and the whole of Chapter II of the Act is an attempt to do those four jobs without paper.

In the wording a student can write in an exam: a signature performs the functions of identifying the signer, evidencing the signer's intention to be bound by or to approve the contents of the document, associating the signer with the document in a way that is difficult to repudiate, and, by the act of signing, bringing home to the signer the seriousness of what is being done; and an electronic method satisfies a legal requirement of signature only if it performs those functions, which is the principle stated in article 7 of the UNCITRAL Model Law on Electronic Commerce.

Why start with the functions

Because the functional equivalent approach cannot be applied to signatures without them. Chapter 70 sets out the method: identify what the paper requirement is for, then ask what an electronic thing must do to serve the same purpose. For writing, the answer was easy, accessibility for subsequent reference. For signature it is harder, because a signature does more than one thing.

And because an examination question about electronic signatures is really a question about these functions. Any answer that begins "a digital signature uses public key cryptography" has started in the middle.

The four functions

Identification. A signature says who. In the paper world it does this badly: a handwritten mark is compared with a specimen, and the comparison is a matter of opinion. It works because forging a particular person's hand consistently is difficult and because most documents are never questioned.

Approval, or animus signandi. A signature says that the signer adopts the contents. This is why a person who writes their name on a page as a heading has not signed it, and why the same mark can be a signature in one place on the page and not in another.

Association with the document. The mark is on the document, so the two cannot be separated. That is why a signed page with a substituted second page is a forgery that people notice, and why each page of an important agreement is initialled.

Ceremony, or the cautionary function. The act of signing marks the transition from negotiating to being bound. It makes the signer pause. The formalities the law imposes on wills and deeds exist largely for this reason, and it is why the Act's First Schedule still excludes a will.

A fifth is often added for commercial documents: the evidentiary function, meaning that the signed document is the record that will be produced later, but that is a consequence of the first three rather than a separate job.