What are digital signatures and why are they used?

What are digital signatures?

In the context of signing documents, digital signatures are the online equivalent of a notarized signature. To apply digital signatures to documents and files the organization must hold a valid digital certificate. Digital certificates are issued by GlobalSign. We are a trusted Certificate Authority and we maintain one of the world's largest and most trusted Public Key Infrastructures (PKI).

When you apply a digital signature, a cryptographic operation binds your digital certificate and the data being signed (e.g., a PDF or Microsoft Office document) into one unique fingerprint. The uniqueness of the two components of the signature are what makes digital signatures a viable replacement to wet ink signatures.

Why are digital signatures used?

  • Authentication – since your third-party validated certificate was used to apply the signature, recipients know it was actually you who signed it

  • Non-repudiation – since your certificate, which is supposed to stay solely in your possession, was used to sign the document, you cannot later claim that it wasn’t you who signed it

  • Content integrity – when the signature is verified, it checks that the data in the document matches what was in there when the signature was applied. Even the slightest change to the original document would cause this check to fail.

What do digital signatures look like?

There are two main types of digital signatures for documents - visible, or approval, and non-visible, or certifying.

Visible/Approval

A visible, or approval, signature appears as a signature line, similar to a wet ink signature, and are used for similar purposes (i.e., signing time sheets, contracts, invoices). Visible signatures can be customized to include an image, such as an image of the signer's wet ink signature or a professional seal or stamp. Multiple visible signatures can be added to each document.

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Example of a visible/approval signature

Non-visible/Certifying

A non-visible, or certifying, signature is not visible within the contents of the document itself, but rather is indicated within the software used to view the document (e.g., as a blue bar along the top of the document in Adobe Reader or as a red ribbon in the status bar in Microsoft Office). Certifying signatures are generally used to lock a document down against future edits and/or provide proof of the document author or origin.

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Example non-visible/certifying signature