Documents such as invoices, contracts or powers of attorney, financial records, and plans, which may contain trade secrets, usually also collect sensitive information. Such documents must be signed so that they remain secure and their integrity and trustworthiness are maintained. This is precisely what Document Signing Certificates do: In today’s article, we will explain what the digital signature is, which regulation clarifies the legal, and how the digital signature works.
What is a digital signature?
The terms “digital signature” and “electronic signature” are often used synonymously. However, it is not the same: The term “electronic signature” is understood to be the digitized counterpart to the handwritten signature. This form of signature is used wherever content in documents or regulations needs to be confirmed.
On the other hand, the digital signature is the equivalent of a notarized signature: a responsible third party, namely the certification body instead of the notary, confirms the identity of the signatory. The verified identity is bound by the certificate authority (CA) to a PKI-based digital certificate (“Document Signing Certificate”). This makes it easy for signers to use digital signatures in electronic documents and cloud-based signing platforms. A digital signature uses a cryptographic algorithm to create a unique digital fingerprint to combine the digital certificate with the digitally signed data. The uniqueness of these different components ensures
The electronic and digital signature thus differ in one significant point: The digital signature guarantees integrity and authenticity to the extent that it can withstand legal proceedings. Due to the cryptographic process, the digital signature verifies and secures:
- The authenticity and the verified source of the document.
- The freedom of manipulation of the record since the digital signature was created. If documents are changed after the signature has been affixed, the signature is displayed as invalid.
- The verification of the identity of the signatory by a trustworthy organization (CA).
Digital signature: different types
The different document services or platforms offer different types of signatures. With Microsoft Word as well as Adobe PDF, we’re looking at two of the most popular:
Sign digitally with Microsoft Word
Microsoft supports visible and invisible digital signatures in its office suite. Similar to a physical document, a signature line appears with the digital visual signature. If several users – for example, two contractual partners – have to sign agreements, this method is usually used.
You will see a blue band in the Word system tray when you open a document with an invisible signature. The invisible signatures are used when the document’s authenticity, integrity, and origin have to be guaranteed without a conventional signature line in the paper. Microsoft provides further information on the signature in Office documents on its in-house support website.
Sign digitally with Adobe PDF
In addition to the certified signature, Adobe also supports the approved signature. Suppose you add a certification signature to a PDF. In that case, this signature not only makes it clear that you are the author of the document and that you have completed the content, but the signature also prevents the document from being tampered with after it has been distributed. If a PDF document is signed in a certified manner, a blue ribbon is visible at the top of the document, which shows the signer’s name and the issuer of the certificate. The security for the authenticity and the authorship of the record is visible.
Approved signatures are intended to accelerate the approval process in companies: The electronic approvals issued by departments or responsible persons are recorded and embedded in the original PDF document. Approval signatures can be individualized to add images such as the handwritten signature or signature details such as place, date, or reason.
This is how the digital signature works
You need an appropriate certificate for legally compliant digital signing: You can obtain so-called document signing certificates from various providers. As the signature creator, you apply for the certificate from your trusted provider and identify yourself. Once this ordering process has been completed, you will soon digitally sign the first documents.
To do this, a hash value is first generated from the message to be signed by you – a special deal that cannot be reversed. The signer encrypts this hash value with his private key and adds the character string, i.e., the signature, to the message. Whoever receives the message can decrypt the signature using the signer’s public key. The task now is to compare the hash value obtained with the hash value calculated from the news. If the values match, the signature is correct: The recipient can now be sure that the identity of the person signing and the integrity of the message or document are guaranteed. On the other hand, if the paper was changed after it was signed or incorrectly signed, the comparison of the hash values yields errors.