Types of Signature Data
Handwritten signatures can be handled electronically in a number of different ways. Each type has its relative merits and it is important to select the appropriate technology to meet specific business requirements. The different types include:
Static Signatures
Also known as Scanned Signatures, these are graphical images obtained by scanning signatures that were written by ink on paper.
Dynamic Signatures
Sometimes referred to as Biometric Signatures, these are captured by signing on an electronic signature pad. Besides the appearance of the signature they record the detailed movement of the pen and a wealth of additional forensic information.
Hybrid Signatures
A Hybrid Signature™ is essentially a dynamic signature but stored in the form of a graphical image that can be more easily handled.
eSeals
Some business practices require the use of corporate stamps or seals, also known as chops, to sign documents.
Florentis products are available to handle all the signature types listed here.
Static Signatures
Static signatures are conventional graphical images that store the visual appearance of a signature. They are most commonly obtained by scanning inked signatures written on paper originals and are sometimes referred to as scanned signatures or signature images.
Static signatures can be handled in a variety of graphical formats. The most commonly used is TIFF, but other types can be used. Florentis products such as the SignPro SSV also allow the of PNG, BMP, JPEG types.
Dynamic Signatures
Dynamic signatures are captured using an electronic signature pad attached to a computer, and they contain two sets of information:
Biometric Data
During signature capture the position of the pen on the signature pad is recorded at discrete time intervals, typically at the rate of 100 or 200 points per second. This information can subsequently be used to reproduce the visual appearance of the signature, and from the timing information it is possible to calculate the speed and acceleration of the pen.
Additional information may also be supplied, depending on the type of signature pad being used. This includes the movement of the pen between strokes, the force of the pen-tip on the surface, and the angle of the pen.
Whatever the capabilities of the signature pad Florentis components store all the information provided in the stored signature data.
Forensic Data
In addition to the biometric information the signature data records details about the signing process and the location at which it took place. This includes the following information:
| Signatory name | The name of the person signing |
| Date and time | When the signature was collected |
| Reason for signing | The text displayed to the person at the time of signing, e.g. “I approve the contents of this document” |
| Type of signature pad | Manufacturer name, model number and version |
| Signature pad driver | Description and version of the signature pad software used to capture the signature |
| Operating System | The type and version of the operating system being used on the host computer, e.g. “Microsoft, ‘Windows XP’;’Professional’;’Service Pack 3’;5.1.2600 |
| Network Interface Card | The unique NIC address, e.g. 000E0C857028 |
| Checksum | The type and value of the hash calculated for the data being signed. This is used to determine whether the document has been changed after it was signed. |
Hybrid Signatures
A Hybrid Signature™ is stored as a conventional graphics image like a Static Signature but in addition retains all the information of a Dynamic Signature.
The disadvantage of dynamic signatures is that they are not automatically recognized by most applications. It is necessary either to integrate the signing capability using one of the Florentis SDKs, or to use one of our ready-to-use add-ins, such as Microsoft Word and Excel.
To overcome this problem, Florentis has developed a Hybrid Signature technology used in the SignOff product. This is a standard graphical image which can be handled widely by applications, but it also contains the full Dynamic Signature which is embedded but not visible. Using this format allows any application to use Dynamic Signature without modification. The embedded data can be displayed using external tools, and the signature can be verified dynamically for maximum reliability.
The disadvantage of hybrid signatures used in this way is that they are not automatically checked and invalidated if the host document changes.
eSeals
There may be situations where a signature pad is not available but a signing process is still required. For this situation the eSeal can be used whereby a handwritten signature is replaced with a controlled, pre-prepared image. In this situation the application is configured to insert the eSeal image in place of a signature. Additionally an eSeal can be merged with a captured signature to provide a graphical background
The Relative Advantages of Static and Dynamic Signatures
Static signatures are very commonly found in office automation systems which scan paper based documents. They can be stored in any graphics format, although TIFF is the most common. Being a standard type they are widely recognized by applications and can be easily inserted into a wide variety of documents.
The disadvantage is that static signatures are limited to visual appearance alone - they do not have any information about the movement of the pen. From a forensic point of view they are highly deficient when compared with the paper based originals which, in the hands of a Forensic Document Examiner, can yield much information about the way in which it was signed, including the order in which the strokes were applied and the direction of the pen.
Dynamic Signatures have significant advantages over both static and paper-based signatures, in that the detailed movement of the pen is recorded and contained within the data. This allows the use of very sophisticated algorithms to verify the authenticity of signatures which makes it very difficult indeed for one person to imitate another. Static signatures can also be verified, but because they lack dynamic data and rely purely on appearance the accuracy can never be as good.
Dynamic signatures also have the advantage of containing forensic information, ensuring the history of the signing is recorded. In addition they typically incorporate a hash of the host document. This is used to determine whether or not the document has changed since signing. In our products this is automatically checked and if the document is found to have changed then the signature is shown crossed-out.