Operation Manual

Table Of Contents

222

Last updated 10/11/2011

Chapter 9: Digital signatures

You use a digital signature, much like a handwritten signature, to approve documents. However, unlike a handwritten

signature, a digital signature verifies your identity to the recipients. A digital signature serves to protect the integrity

and authenticity of a document as of the time it was signed. A digital signature on a PDF document may include a

photo, image of your handwritten signature, or other personal details. Document authors can attest to the contents of

their documents by adding a certifying signature.

About digital signatures

A digital signature, like a conventional handwritten signature, identifies the person signing a document. Unlike a

handwritten signature, a digital signature is difficult to forge because it contains encrypted information that is unique

to the signer. It can be easily verified and informs recipients whether the document was modified after the signer

initially signed the document.

To sign a document, you must obtain a digital ID or create a self-signed digital ID in Acrobat or Adobe Reader. The

digital ID contains a private key and a certificate with a public key and more. The private key is used to create the digital

signature. The certificate is a credential that is automatically applied to the signed document. The signature is verified

when recipients open the document.

When you apply a digital signature, Acrobat uses a hashing algorithm to generate a message digest, which it encrypts

using your private key. Acrobat embeds the encrypted message digest in the PDF, certificate details, signature image,

and a version of the document when it was signed.

Digital signature in a PDF form

Additional resources

For videos and articles on digital signatures, see these resources:

• Using Digital Signatures in a PDF File: www.adobe.com/go/lrvid_029_acrx_en

• How to Digitally Sign a Document with Adobe Reader: www.adobe.com/go/lrvid_030_acrx_en

• Digital Signatures in PDF and Acrobat: www.acrobatusers.com/tutorials/digital-signatures-pdf-acrobat

• Security Matters (Adobe blog): http://blogs.adobe.com/security/

• Content Security Library which contains quick keys, enterprise user guides, and other technical resources:

learn.adobe.com/wiki/display/security/Document+Library