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Digital signature

A digital signature (also called an electronic signature) is the equivalent of a handwritten signature. The eIDAS regulation of the European Union distinguishes three quality levels of electronic signatures.

What is a digital signature?

A digital signature is a modern alternative to signing documents with paper and pen.

A digital signature uses advanced mathematical technology to verify the authenticity and integrity of digital messages and documents. It guarantees that the content of a message is not altered during transmission and helps us overcome the problem of impersonation and tampering in digital communication.

A digital signature also provides additional information such as the origin of the message, its status and the signer’s consent.

Digital signature and its importance

In most region of the world, digital signatures are considered legally binding and have the same value as traditional signatures on documents.

In addition to signing digital documents, digital signatures are also used in financial transactions, email service providers, and software deployment, areas where the authenticity and integrity of digital communications is critical.

The so-called public key infrastructure, ensures the authenticity and integrity of the data in a digital signature.

How does the digital signature work?

Using a mathematical algorithm, digital signature providers generate two keys: a public key and a private key. When a signer digitally signs a document, a cryptographic hash is generated for the document and the digital signature.

This cryptographic hash is then encrypted with the sender’s private key, which is stored securely. It is then appended to the document and sent to the recipient of the digital signature along with the sender’s public key.

The recipient can decrypt the encrypted hash using the sender’s public key certificate. A cryptographic hash is again generated on the receiver side.

Both cryptographic hashes are compared to verify the authenticity of the document. If they match, the document has not been tampered with and thus the digital signature is valid.

Types of digital signature

Digital signatures are differentiated into different security levels by the requirements for the respective certificates and the issuing certification authority precisely formulated in the “eIDAS” regulation.

  1. Simple Electronic Signature The simplest form of a digital signature is described by the legislator as “data in electronic form that is attached to or logically linked with other data in electronic form and that is used by the signatory to sign”. In concrete terms, this means that, for example, even a document signed by hand that has been scanned and thus digitized has a simple electronic signature. This is because it is the electronic equivalent of a handwritten signature, with which the signatory expresses his or her agreement with the content of the document in question. This form of digital signature has a low level of security.

  2. Advanced Electronic Signature The requirements for the advanced electronic signature, as described in Article 26 of the eIDAS Regulation, go beyond this. This significant type of digital signature is uniquely associated with a signer, as it ensures the identification of the signer. At the same time, it must be ensured that the content of a signed document cannot be subsequently changed without this becoming immediately apparent and thus rendering the document invalid. In summary, the advanced electronic signature both guarantees the integrity of the document and proves the authenticity of the signatory beyond doubt.

3 Qualified Electronic Signature The qualified electronic signature is the highest form of digital signature. It has the highest legally binding value and is equivalent to a handwritten signature in all EU member states. In Article 3, eIDAS defines a qualified electronic signature as “an advanced electronic signature created by a qualified electronic signature creation device and based on a qualified electronic signature certificate.” The following fundamentals are required for this digital signature:

  • The existence of a digital identity, such as can be obtained in various identification procedures from private and government providers.
  • a qualified certificate from a state-approved trust service provider, a so-called trust center, which gives the signed document its unique legal status.

Digital signature and its areas of application

The range of applications for the digital signature is broad and can be found in practically all areas of society. Companies use the digital signature for internal and external signature processes. Unlike analog signature processes, these processes do not require paper, scanners or printers. Digital signatures allow the process to be completely digitized.

A widespread application of the digital signature is simple approvals in business processes. On the other hand, employment contracts, large purchase orders and generally everything that has a high legal value in case of doubt are signed digitally with a qualified certificate. Digital signatures generated in this way stand up to legal scrutiny worldwide because they are equivalent to handwritten signatures in all respects. The areas of application of the digital signature also extend to the private, public and business sectors.


The advantages of digital signature, such as a high level of security, paperless online transactions, reduction of cost and effort, increased productivity and efficiency, remote access, and better usability, make it a highly trusted and secure way to conduct electronic transactions or exchange information over the Internet.

It can be used by ordinary citizens, businesses and government agencies for business or other legal purposes. It is used in many forms, such as a digital signature attached to a document, a digital certificate, to encrypt the entire document, or simply to sign an email. The digital signature is unique and cannot be copied, which is its greatest advantage as it binds the digital document to the owner of the sender of the data.

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