An electronic signature can be as simple as a typed name or a digitized image of a handwritten signature that is placed on the PDF. The controlling document for Electronic Signatures is The Electronic Signatures in Global and National Commerce Act (E-Sign Act). The official definition:
“Electronic Signature” – The term “electronic signature” means an electronic sound, symbol, or process, attached to or logically associated with a contract or other record and executed or adopted by a person with the intent to sign the record.
The problem is that there is no mention of establishing the identity of the signer, nor regards to maintaining the integrity and security of the E-signed document.
This is where the Digital Signature comes in. A digital signature creates an electronic “fingerprint” in the file. Everything (characters, images, etc.) in the document are processed to create a unique hash that is locked with a private key and stored inside the document. Any change to the document alters the hash and invalidates the digital signature, thereby protecting against signature forgery and information tampering.