Broadly put, an electronic signature is digital information that corresponds very accurately to the handwritten signature from which it was captured. In other words, it is an electronic record of the performance of a physical signing action (just like its traditional ink-on-paper cousin). It is important to make a distinction between an electronic signature and an image – electronic signatures are not images, and vice versa. Just like a photocopy or photograph of your handwritten signature does not imply that you have necessarily consented to the terms of a written agreement, an easily copied-and-pasted digital signature image does not imply that its creator has consented, either. Original and unique biometric and forensic signature data is required for both paper-based and electronic signature records to be valid and enforceable in court (link to electronic signature forensics information).

What an electronic signature is actually comprised of differs slightly depending on what system is being used. This can make a big difference if an electronic signature should be challenged in a court of law. Generally, the pen data of the handwritten signature (the so-called “biometric” data) are captured. Some capture systems immediately generate an image based on this information, then immediately discard the raw signature data. Then, based on the image, subjective inferences are made about the characteristics of each signature stroke. While this method may suffice to “keep honest people honest,” it is doubtful that electronic signatures captured via this method could survive examination and scrutiny in a court of law, since the biometric and forensic information is not present in the signature file. When dealing with high-value transactions such as mortgages, business agreements, and insurance contracts, a more robust and secure electronic signature system may be necessary.

A second, more robust method captures pen events and position at a high rate of speed. This pen event data can then be encrypted in order to bind it to the document data to be signed. Later, if desired, image files can be generated from this data for display purposes without any loss of information or resolution of the original electronic signature record. The second method is a more robust and valuable method of collecting electronic signatures because it preserves the original forensic data that is present in a handwritten signature, and is far more likely to survive scrutiny in a legal setting as a result. Additionally, this method does not necessitate a cost any higher or lower cost than other methods, so price should not have to be a factor in its implementation. Topaz Systems is one supplier that utilizes this method. On their website, they feature several useful pages of information about their electronic signature systems as well as links to various white papers and guidelines for electronic signature capture.