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Digital signatures have become indispensable in our increasingly digital world. But have you ever wondered how they actually work behind the scenes? In this comprehensive guide, we’ll explore the intricate technical processes that make digital signatures secure, legally binding, and widely trusted across industries.
What is a digital signature?
A digital signature, which should not be confused with a digital certificate, is a mathematical technique used to validate the authenticity and integrity of a message, software or a digital document.
A digital signature, as opposed to a traditional signature, is not a name but two “keys” or sequences of separated characters. It applies cryptographic measures to the content of a message or document in order to show the following to the message’s recipient:
- The sender of the message is real (authentication);
- The sender cannot deny that they sent the message (non-repudiation);
- The message has not been altered since it was sent (integrity).
The cryptographic foundation of digital signatures
At its core, a digital signature relies on asymmetric cryptography, also known as public-key cryptography. This sophisticated system uses a pair of mathematically related keys:
- Private key: Kept secret by the signer, used to create the signature
- Public key: Shared openly, used by others to verify the signature
The beauty of this system lies in its mathematical relationship: what one key encrypts, only its pair can decrypt, and vice versa.
A digital signature is a key part of the advanced electronic signature and qualified electronic signature, but not of the simple electronic signature.
What is the difference between digital signatures and electronic signatures?
Digital and electronic signatures are often used as synonyms, but not all types of electronic signatures have the same security features as truly digital signatures.
A simple electronic signature would be, for example, a personal identification number (PIN) entered at a cash machine or clicking on “accept” or “do not agree” on a “terms and agreements” electronic contract.
This type of electronic signature cannot attribute the electronic signature of a signatory to a specific signatory, therefore, it is does not have the same features as a digital signature.
All digital signatures are electronic, but not all electronic signatures are digital.
A digital signature is legal, but its aim is not to attest to the signatory’s willingness like an electronic signature, but just to encrypt the data of a document to give it greater security.
Also a digital signature can be used for a wider range of file types, such as videos, sound, music, etc., making it more versatile than the traditional paper signature.
Step-by-step: How digital signing works?
1. Document hashing
When you sign a document digitally, the process begins with creating a unique “fingerprint” of your document called a hash. This hash is generated using algorithms like SHA-256, which converts your entire document into a fixed-length string of characters. Even the smallest change to the document would result in a completely different hash.
2. Signature creation
The hash is then encrypted using your private key, creating the digital signature. This signature is unique to both the document and your private key, ensuring that:
- Only you could have created it (authentication)
- The document hasn’t been altered (integrity)
- You cannot deny signing it (non-repudiation)
3. Document packaging
The digital signature is then embedded into the document along with your digital certificate, which contains your public key and identity information verified by a trusted Certificate Authority (CA).
Practical requirements and setup
One of the greatest advantages of digital signatures is their simplicity from a user perspective. The technical requirements are minimal:
Hardware requirements
- Any modern device: computer, smartphone, or tablet
- Internet connection
- No special hardware like card readers or USB keys required
Software requirements
Most digital signature solutions work through web browsers, eliminating the need for specialized software installation. Users simply need access to their email and a standard web browser.
User experience: The signing process
For end users, the signing process is remarkably straightforward:
- Receive notification: Get an email with a secure link to the document
- Access document: Click the link to view the document requiring signature
- Review content: Read through the document thoroughly
- Confirm intent: Check a confirmation box indicating agreement
- Verify identity: Often through SMS code or other authentication methods
- Complete signature: The digital signature is applied automatically
- Receive confirmation: Get the signed document via email or secure client portal
Compatible documents and common use cases
Digital signatures work with a wide variety of document types, making them versatile for numerous business scenarios:
Document types
- Contracts: Employment agreements, service contracts, partnerships
- Real estate documents: Lease agreements, property sales contracts
- Business documents: Purchase orders, delivery receipts, invoices
- Financial documents: Loan agreements, insurance policies
- Legal documents: Wills, legal notices, court filings
- HR documents: Onboarding paperwork, policy acknowledgments
Industry applications
Digital signatures have found widespread adoption across sectors including healthcare, finance, legal services, real estate, and government agencies, where document integrity and legal compliance are paramount.
European standards: PDF as the gold standard
In Europe, regulatory frameworks have established PDF as the only recognized standard for digitally signed documents. This standardization ensures:
- Universal compatibility: Documents can be opened and verified across different systems
- Legal recognition: Courts and authorities accept PDF-based digital signatures
- Embedded security: All signature elements are contained within the PDF file itself
- Long-term preservation: Documents remain verifiable over extended periods
This PDF requirement means that all signature elements—including certificates, timestamps, and cryptographic data—must be embedded directly within the PDF file structure, ensuring document portability and long-term integrity.
Security layers in digital signatures
Certificate Authorities (CAs)
Digital certificates are issued by trusted Certificate Authorities who verify the identity of certificate holders. This creates a chain of trust that validates the authenticity of signatures.
Timestamping
Many digital signature implementations include trusted timestamps, which prove when a document was signed. This prevents issues with expired certificates and provides additional legal protection.
Advanced signature formats
Modern digital signatures often use advanced formats like PAdES (PDF Advanced Electronic Signatures) that provide additional security features and long-term validation capabilities.
Legal framework and compliance
Digital signatures operate within robust legal frameworks:
- eIDAS regulation (EU): Provides legal recognition for electronic signatures
- Electronic Signatures Act (US): Establishes legal validity of electronic signatures
- International standards: ISO/IEC standards ensure global interoperability
Benefits of understanding the process
Understanding how digital signatures work helps users:
- Trust the technology: Knowledge builds confidence in digital processes
- Ensure compliance: Better adherence to legal and regulatory requirements
- Troubleshoot issues: Identify and resolve signature verification problems
- Make informed decisions: Choose appropriate signature solutions for specific needs
Digital signatures represent a sophisticated blend of cryptographic security and user-friendly design. By leveraging public-key cryptography, hash functions, and trusted certificate authorities, they provide a level of security and authenticity that often exceeds traditional handwritten signatures.
The combination of robust technical foundations with simple user requirements makes digital signatures an ideal solution for modern document workflows. Whether you’re signing a simple contract or a complex legal document, the underlying process ensures your signature is secure, verifiable, and legally binding.
Ready to implement secure digital signatures in your workflow? Try Signaturit today and experience the perfect balance of security, simplicity, and legal compliance that digital signatures offer.
If you want more information, get in touch with our team to get personalised advice.
FAQ: Digital Signatures Explained
How do I create a digital signature?
To create a digital signature, you’ll typically need a digital signature provider or software (like Signaturit, Adobe Acrobat, or DocuSign). These platforms guide you through uploading a document, applying your signature, and validating it using your digital certificate or credentials.
How do I insert a digital signature in a PDF?
Most PDF software (e.g., Adobe Acrobat) allows you to insert a digital signature by:
- Opening the document.
- Selecting “Fill & Sign” or “Certificates.”
- Choosing “Digitally Sign,” then placing your signature in the designated field.
You’ll need a digital certificate to complete the process, often issued by a trusted certificate authority (CA).
Can a handwritten signature be digital?
Yes, a handwritten signature can be captured digitally, for example using a stylus or touchpad. However, while visually similar to a wet ink signature, this alone doesn’t make it a digital signature unless it’s combined with cryptographic validation.
Can I just type my name as a digital signature?
Typing your name can count as an electronic signature, but not a digital signature in the cryptographic sense. A typed name may be legally valid in many jurisdictions, but lacks the tamper-evident and identity-verification features of a true digital signature.
Does a digital signature need to be notarized?
In most cases, no. A digital signature backed by a valid certificate already meets legal standards for authenticity. However, for certain regulated documents (like deeds or affidavits), notarization may still be required depending on jurisdiction.
