# About Signatures

You can sign a DocuWorks document in the same way as you would put a seal on or sign a paper document.

## Purpose of digital signatures

When documents are signed, it is possible to confirm their signers and the contents of the documents at the point when they were signed, thus preventing forgeries or falsifications.
In DocuWorks, you can add a digital signature to a document to indicate that you created it or approved of its contents, just like you would sign a paper document.
With paper documents, you can easily confirm the signer and the date that it was signed by looking at it. With a digital signature, you can confirm the identity of the singer and whether the document has been modified since it was signed, by acquiring the proof information for the signature and verifying the signature. If the document has more than one signature, you can confirm the order in which the document was signed.
You can also restore the document to the state immediately before or after each signature was added.

## Signature modules

The shape of a digital signature and information therein differ depending upon the type of a signature module used.
DocuWorks Electronic Signature
You can use an Electronic Signature from an Electronic Signature Case to sign documents. You can also verify the trustworthiness of an Electronic Signature by comparing the Electronic Signature-impression on a document with an Electronic Signature in the Electronic Signature Case. The DocuWorks Electronic Signature implements a public key cryptosystem based on the asymmetric algorithm.
Digital Certificate
You can sign a document using a Digital Certificate issued by a Certification Authority (CA). A person who received a signed DocuWorks document can take the signer's public key out of the certificate to verify the signature. By verifying the signature, you can confirm that the DocuWorks has not been altered since it was signed and that the signer is the actual owner of the private key.

## Signed documents

A signed DocuWorks file is shown with a signature mark in thumbnail view of Desk.
Note
DocuWorks Electronic Signature does not use Digital Certificates issued by Certification Authority. When you print DocuWorks documents marked with the DocuWorks Electronic Signature imprint or the signature image of a Digital Certificate onto paper documents, the paper documents cannot be used as legal deeds or signed documents.