For the sake of privacy and legal enforceability, an electronic signature must remain under the “sole control of the signer” to be valid under the national ESIGN electronic commerce law. To satisfy this requirement, a signature must be placed or linked into the relevant document directly, with no interlopers or copies, and then bound to the document in such a way as to render document tampering detectable. Without these critical features, it would not be possible to prove that a signatory did indeed assent to the terms of the written agreement or that the language in the document was identical in form to the state in which it was initially signed.

On the other hand, there is value in monitoring and evaluating the integrity of data received from a signature pad, such as the point sampling rate, and detection of unusual time-related activity in signing.

Document security and signature binding are also important. If the signature is not linked to the contents of the written agreement, it has no real value since there would be no evidence of tampering or changes made to the terms post signing.