What is a Digital Signature?

Your complete guide to Digital Signatures, PKI, Digital Certificates, and how they work

Feb 9, 2021
What is a digital signature

Signing your document with a Digital Signature is the most seamless and secure way to complete an agreement. Businesses and institutions are switching to Digital Signatures for a safer, more efficient, and paperless way to sign. So, what is a Digital Signature? Read on to find out.

What are Digital Signatures?

A Digital Signature is a specific type of Electronic Signature (e-Signature). More advanced than the standard Electronic Signature, Digital Signatures provide a type of digital ID which is unique to the person who is signing a document. In order for a document to contain a valid Digital Signature, it needs to prove that:

  • It was signed by the signer
  • The document wasn’t tampered with by anyone else in the signing process

To do this, Digital Signatures use Public Key Infrastructure (PKI), Digital Certificates and Qualified Timestamps to guarantee the highest level of security and legal acceptance worldwide.

Most e-Signing services offer the option to choose between signing with an Electronic Signature or a Digital Signature. To learn more about the difference between the two signature types and their uses, check out this page.

What is PKI?

Public Key Infrastructure (PKI) is a term which refers to everything needed to manage Digital Certificates in Public Key Cryptography.

It’s a framework for businesses to establish a secure web of trust in which they can exchange signed documents between different users and web servers. PKI depends on Digital Certificates to verify the authenticity of the agreement.

What is a Digital Certificate?

Creating a valid Digital Signature using PKI requires a Digital Certificate. Sometimes known as a Public Key Certificate or Digital ID, a Digital Certificate is an electronic document used in Public Key Cryptography to verify an identity, such as a person signing a document.

Public Key Cryptography - also known as Public Key Encryption - works with cryptographic key pairs: Private Keys and Public Keys. These key pairs are used to encrypt and decrypt data. Once data is encrypted by one of the keys, it can only be decrypted by its key pair.

A Digital Certificate binds an identity to a key pair. Watch ComputerPhile’s video to learn more:

In other words, a Digital Certificate acts like a form of electronic identification for the person signing the agreement. Usually Digital Certificates are issued by a trusted third party called a Certificate Authority (CA) who holds the Public Key.

How does it work?

Combining everything that we’ve learned, let’s use iLovePDF’s Sign PDF tool as an example. To create a Digital Signature through iLovePDF, the process goes like this:

  1. When a person signs a document, iLovePDF converts all the signing data into an encrypted message. This is known as a hash value.
  2. iLovePDF encrypts the hash value with the signer’s Private Key and creates a Digital Signature.
  3. The signed document is received by the CA who uses the Public Key to decrypt it and verify that it was the signer who encrypted it.
  4. The CA issues a Digital Certificate which verifies the signer’s identity. The Digital Certificate is embedded in the signed document, along with a Qualified Timestamp.
  5. Success! The document has been signed using a valid Digital Signature in a secure connection.
  6. PDF Signature

Qualified Timestamp for stronger legal validity

In addition to the Digital Certificate, Certificate Authorities also attach a Qualified Timestamp to the signed document. A Qualified Timestamp is a technology adopted by the European Union to record the exact date and time at which the document was signed by the signer.

This ensures no further modifications have been made to the document since it was signed, strengthening its legal validity.

A brief summary...

As you can see, Digital Signatures rely on quite a technical framework to guarantee the authenticity and legal validity of your signature on a document. That’s why Digital Signatures are used all over the world to complete important business transactions.

To sum up what we’ve learned, here are the key points to take away with you:

  • A Digital Signature is special type of Electronic Signature
  • Digital Signatures use PKI to establish a secure connection
  • PKI relies on Digital Certificates to verify the signer’s identity
  • A Qualified Timestamp strengthens a documents legal validity

Now that you know everything about Digital Signatures, it’s time to get signing! Start signing with a Digital Signature here.

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