How it works digital signatureIt uses asymmetric cryptography, digital certificates, and hash functions to authenticate the signatory, protect document integrity, and ensure legal validity. The process involves key generation, identity association, signing, and public key verification.
The digital age has brought with it a revolution in how digital signatures work, and everything related to information and documents. In the business and legal spheres, the need to sign contracts, agreements, and other records persists, but pen and paper are being robustly replaced by an innovative technology: the digital signature.
In this article, we'll discuss how digital signatures work, revealing the key elements that make this method secure and reliable. Let's get started?
Summary
- Technical concept of digital signature and its cryptographic basis.
- Process steps: key generation, hashing, signing, and verification.
- Differences between digital signatures and traditional signatures.
- The role of digital certificates in authentication.
- How to sign documents in Word, PDF, and WhatsApp.
- Complete guide to signing digitally using the ZapSign platform.
Quick facts
- The electronic signature sector is expected to grow at a CAGR of 39,3% through 2034, according to an analysis presented in 2025. Source: global e-signature statistics.
- 77% of European countries had fully implemented eIDAS by 2021, strengthening digital authentication standards. Data from European Comission.
- Digital signatures reinforce authenticity, integrity, and non-repudiation, according to analyses by NCCIC/CISA. Details at [link/reference]. guidelines on digital signatures.
The rise of digital signatures in the business world
As companies seek to optimize processes and speed up transactions, digital signature emerges as an essential tool, providing an efficient and secure approach to dealing with formality documentary.
The growing dependence on the digital environment and the search for more agile solutions have driven the widespread adoption of digital signatures in business scenarios.
As digitalization continues to shape the corporate landscape, the digital signature market is establishing itself as an indispensable ally in the relentless search for innovation and operational efficiency. Proof of this is that, According to research, it will grow almost 30% by 2030, reaching the mark of 40,23 billion dollars.
What is a digital signature and how does it work?
How digital signature worksIt authenticates documents through asymmetric cryptography, digital certificates, and hash functions, ensuring integrity, authenticity, and legal validity in electronic processes.
Unlike a paper signature, it is based on complex cryptographic engineering, using public and private keys.
It also uses digital certificates: seals of authenticity that validate the link between the public key and the signatory's identity, giving the digital signature legal reliability.
How digital signatures work (technical steps)
The technical functioning of digital signatures involves the use of cryptographic algorithms and the generation of key pairs, along with the use of hash functions to guarantee the authenticity and integrity of documents. Check it out below.
1. Key pair generation
The process begins with the creation of a pair of asymmetric keys: one private and one public. These keys, generated by specific algorithms, have a unique mathematical relationship. The private key is kept confidential, while the public key can be shared.
2. Association with identity
The holder of the private key can associate it with an identity through a digital certificate issued by a Certification Authority (CA): a kind of “seal of approval” of the authenticity of the public key and, by extension, the digital signature.
3. Hash generation
When signing a digital document, the signer uses a hash function on the file contents. The document data is transformed into a fixed-length string of characters, called a hash. Even minimal changes to the document generate significantly different hashes, ensuring the integrity of the content.
4. Signing with the private key
The signer's private key is used to sign the generated hash. This creates a unique digital signature for that specific document. The signature is essentially a sequence of bytes that, when decrypted with the corresponding public key, can be verified as authentic.
5. Inclusion of the signature in the document
The digital signature, along with the digital certificate (if applicable), is then incorporated into the document. This inclusion can take different forms depending on the file format, but generally involves adding metadata that represents the signature.
6. Signature Verification
The document receiver uses the signatory's public key to decipher the digital signature, thus recovering the original hash. It then applies the same hash function to the document content and compares the hashes. If they are identical, the signature is considered valid.
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Main technical differences of digital signatures
The primary distinction of the digital signature lies in some fundamental pillars to ensure the security, authenticity and legal validity of electronically signed documents.
Cryptography
Digital signature uses asymmetric encryption with private and public keys. The private key creates the signature, while the public key verifies authenticity. The process also involves hash functions, ensuring uniqueness and, thus, the integrity of the signed document.
Electronic Certificates
The digital certificate validates the signatory's identity, ensuring the legitimacy of the signature. It also provides legal backing by establishing a chain of trust from the Certificate Authority to the signer.
Security and non-repudiation
Digital signature security is enhanced by asymmetric encryption and hash functions, making forgery difficult. The presence of the digital certificate strengthens non-repudiation, preventing the signatory from denying the signature, as the association with their identity is validated by the certificate.
| Technical criteria | Digital signature | Electronic signature |
|---|---|---|
| Technological base | Asymmetric cryptography and hashing | Insert image or click |
| Electronic Certificates | Mandatory (ICP-Brasil or equivalent) | Not obligatory |
| Legal validity | Elevated, with non-repudiation | It can vary depending on the context. |
| document integrity | Ensures cryptographic verification. | Without integrated verification |
⚠️ Also check out these related articles 👇
➡️ Learn how to sign with a digital certificate
➡️ Understand what a digital signature verifier is for
➡️ What is a digital contract and how to adopt one for your company
Digitally signing Word and PDF files
To sign documents in Word, native resources or external tools, integrated with cloud storage platforms, can be used.
For PDF documents, Adobe Acrobat is the most common, allowing the creation and application of signatures through the “Tools” and “Sign & Certify” options.
Digital Platforms online also offer similar services, facilitating the process by uploading the document.
Signing digitally via WhatsApp
To sign via WhatsApp, you must have a scanned version of the document. Using a digital signature tool, the signature is created and saved as an image. This image can be sent via WhatsApp to the person responsible for the signature, who incorporates it into the digital document using appropriate tools.
Although WhatsApp does not have specific functionality for digital signatures, this method is practical, as long as both parties confirm the authenticity and agree to the use of the image in the legal context of the region. The use of reliable tools is essential to ensure process safety.
How digital signatures work with ZapSign (step-by-step)
ZapSign has a own digital signature platform. With a simple, intuitive and highly uncomplicated interface, the tool offers a solution capable of simplifying the entire process of signing electronic documents.
Below, a step-by-step guide with everything about how to make digital signature by ZapSign.
Step 1 – Log into the system
First, you must access the our website, and inform your login and password, to then be forwarded to the main page.
Step 2 – Generate a new document
On the ZapSign dashboard, click the “NEW” button to go to the next screen and generate a new document.
Step 3 – Upload the .PDF file
By clicking on “select document”, you will be able to upload the document to be signed. This document must be in format PDF.
Step 4 – Sign with digital certificate
Select the “Advanced Authentication” option after uploading the file.
Enter the names of the signatories in the field below “Who will sign”. If the signatories are already added to your contact list, click on the “Contacts” option to select and insert them. This option is located below the area for entering the names of signatories.
Tap the “Authentication Method” option and “Digital Certificate”.
Step 5 – Add your own signature to the document
If your own signature is also required for document validation, click on the “I will sign” option, enter your name there and tap on the “Continue” button to proceed to the next screen.
Step 6 – Sort between subscriptions and visas
Position the places on the document where signatures and visas should be inserted by clicking on the chosen space, right after the signatory's name, and choosing between signature or visa.
Click on “Save and Continue”.
Step 7 – Generate and send the subscription links
If contact with your signatory is made via WhatsApp, you must click on the button with the app's logo and send the link directly to the person.
If the chosen medium is another, no problem: just go to the blue icon next to the link to copy it and, later, paste it wherever you prefer.
The option to send your document by email is also available. In this case, tap the “Enable automatic email sending” option and enter the email addresses of the people who will subscribe.
Step 8 – Sort the signatories
If it is necessary to establish a specific order for the signatures, this can be easily done using the “Order signatures” button. This way, the order will be defined by dragging the names of the signatories on the screen to the appropriate positions. Each signatory will only receive their notification email, advising them to sign the document, when the previous signatory has already signed it.
Step 9 – Finish the procedure
Finally, you can create a personalized message to be sent along with the notification email, in addition to activating notifications with reminders for those who have not yet subscribed.
Click “Send and finish” and that’s it! The document was generated and sent to the respective signatories.
From there, you can follow the progress of the signatures, as your signers open the link and sign the file.
Step 10 – Your signers sign the document
Each signatory must click on the document's signature link, read it very carefully and, in agreement with its terms, click on the “Sign” option.
Some information from the signatory will be requested for the purpose of verifying their identity: full name, email and telephone number.
Then, they must click on “Continue” and sign with their finger, mouse, capacitive pen or in the way that best suits the device used.
By tapping “Finish”, the signature will appear at the end of the document, in the signature report, and also in other places where you have placed it.
By following the 10 steps in this guide, you will have no difficulty using our platform perfectly.
If you're ready to simplify and improve the digital signature process for your documents, ZapSign is available to help. Click here to speak to one of our consultants and discover the solutions that will make your experience more efficient and safe.
Frequently Asked Questions (FAQ)
How is a digital signature created?
A digital signature is created by generating a hash of the document, encrypting it with the signer's private key, and then verifying it with the corresponding public key.
What is required for a digital signature to be valid?
The use of a digital certificate, asymmetric cryptography, and proper verification is necessary to guarantee the authenticity, integrity, and non-repudiation of the document.
How do I add a digital signature to a document?
The signature can be applied to digital signature systems, PDF platforms, or applications that support digital certificates and verification functions.
Is it valid to sign a contract using a digital signature?
Yes. When associated with a digital certificate and appropriate verification methods, a digital signature has legal validity and guarantees the integrity and identity of the signatory.
What is the difference between a digital signature and an electronic signature?
A digital signature uses cryptography and a digital certificate to validate identity and integrity. An electronic signature can be just an image or confirmation, without cryptographic verification.
Getúlio Santos is the CEO of ZapSign, a lawyer, technology enthusiast, and entrepreneur.
