Difference Between Digital Signature and Digital Certificate: A Complete Guide

For example, when a person digitally signs a PDF , the signing system combines information from the document and the signer's private key to generate the digital signature. The recipient can then verify the signature with the corresponding public-key information.

Electronic signatures are employed to:

Commercial contracts

Invoices

Government Forms

Electronic tendering

Filings with tax and regulatory authorities

Employment records

Compliance and legal documentation

Electronic approvals

Secure business communications

The main purpose of a digital signature is thus related to the signing, authentication and integrity of documents.

What Is a Digital Certificate?

A digital certificate is an electronic credential that associates a public cryptographic key with an identity. It is generally issued by a trusted Certificate Authority (CA) after the necessary identity verification process is completed. The certificate contains information that allows systems to identify who or what the public key belongs to.

Information that can be included depends on the certificate type:

Name or identity of the certificate holder

Public Key

Certificate Authority

Expiry period

Serial number of certificate

Crypto information

Digital signature of the authority issuing it

The certificate is thus an important part of the establishment of trust in a public-key infrastructure.

This highlights a key difference between digital certificates and digital signatures, as certificates are primarily used to prove identity and build trust in a public key, whereas signatures are generated by cryptographically signing electronic information.

Digital Signature and Digital Certificate: How Are They Connected?

In many certificate-based signing systems the digital signature and digital certificate go hand in hand.

The process is simplified as:

Identity verification → Digital certificate → Public / private key pair → Digital signature → Signature verification

Let us say that an authorized employee has to sign a business document digitally. The employee has a digital certificate containing a public key. The signer keeps the corresponding private key in a secure manner.

The certificate is used to establish trust in the public key. The digital signature is the cryptographic evidence that is attached to the signing of the document. Thus, the terms are sometimes confused. These are related technologies, but you should not use one as a replacement for the other.

Difference Between Digital Signature and Digital Certificate

The difference between a digital signature and a digital certificate becomes clear when understanding how each is used.

1. Objective

Digital Signature: Uses electronic information to sign it to help authenticate and verify its integrity.

Digital Certificate: To bind an identity to a public key so that it can create trust.

2. Main Function

Digital Signature: Can identify the signer and can tell if the information that was signed has been changed.

Digital Certificate: A digital certificate is used to establish trust in the public key and in the identity of the owner of the certificate.

3. Created/Issued By:

Digital Signature: The digital signature is created during the signing process using the signer's private key.

Digital Certificate: Issued by a trusted Certificate Authority (CA) after the required verification process.

4. Legend to Associations

Digital Signature: Cryptographically signing the document with the signer's private key.

Digital Certificate: Contains or points to the public key of the certificate subject.

5. Typical Uses

Digital Signature: Used to sign documents, forms, contracts, invoices and electronic transactions.

Digital Certificate: Used for identity verification, safe communication, document signing, and other cryptographic applications.

6. Document Completeness

Digital Signature: Verifies that the signed content has been modified after signing.

Digital Certificate: It alone does not provide evidence that a given document has not been altered.

7. Confirming Identity

Digital Signature: Links the signer to a signed document or electronic data.

Digital Certificate: Binds a public key to verified identity information.

8. Validity

Digital Signature: It is validated against the signed information and applicable signature-validation conditions.

Digital Certificate: Contains its own validity period and can also have a status such as valid, expired or revoked.

We can say:

Digital Signature = Signing and verifying electronic data

Digital Certificate = Identity & trust are created

Digital Signature + Digital Certificate = Secure Certificate Based Digital Signing Process

How Does a Digital Signature & Digital Certificate Work Together?

Digital signatures and digital certificates are parts of a public-key cryptography and trust framework that are complementary to one another. The digital signature usually generates a cryptographic hash over the pertinent data and encrypts this data with the signer's private key so that it can create the digital signature when a document is digitally signed. The matching public key can then be used to verify the signature and to verify whether the document has been changed after signing.

A Digital Certificate helps establish the identity to which that public key belongs. It is issued by a Certificate Authority after the necessary verification process. It contains relevant identity and public key information. The certificate is also digitally signed by the issuing authority and compatible software can verify that it was issued by a trusted authority and that it is still valid.

The Digital Certificate helps to establish trust in the identity of the signer and the public key and the Digital Signature helps to authenticate the signed information and to protect its integrity.

What Is Digital Signature and Digital Certificate Used For?

Both technologies have applications across digital business and security, but their uses can differ.

Uses of Digital Signatures

Electronic signatures are very useful when a person or organization needs to sign or approve electronic information.

Typical instances are:

Signing of PDF documents

Signing agreements

Invoice approval

E-tendering

Government response

Regulatory filings

Approvals from Corporates

Electronic contracts

Safe e-transactions

Applications of Digital Certificates

Digital certificates can be used across many areas of digital security depending on the type of the certificate.

Examples are:

Identity verification

Secure messaging

Website security

Email security

Signing papers

Code signing

Enterprise security

Public Key Infrastructure

So when asking what is digital signature and digital certificate, one needs to look at their roles and not at two names for the same technology.

Digital Certificate vs Digital Signature: Which One Do You Need?

The answer depends on what you are trying to accomplish.

If your requirement is to sign a document electronically, you may need a digital-signing mechanism.

If your requirement involves establishing trust in a public key and identifying its owner, a digital certificate is an important component.

For certificate-based document signing, the two generally work together rather than being alternatives.

For example, an organization may use a digital certificate to establish the identity associated with a signing key and then use the corresponding private key to create digital signatures on business documents.

Common Misconceptions About Digital Signatures and Certificates

A Digital Certificate Is a Digital Signature

Not exactly. A certificate helps establish identity and trust around a public key. A digital signature is created when electronic information is cryptographically signed.

A Signature Image Is Always a Digital Signature

No. A scanned or drawn signature placed on a PDF is generally a visual or electronic signature. It should not automatically be treated as a certificate-based digital signature.

A Certificate Automatically Signs Every Document

No. A certificate can be used as part of a signing process, but a document must actually be signed for a digital signature to exist.

Digital Signatures Cannot Become Invalid

Digital-signature validation can depend on several factors, including changes to the document, certificate validity, trust configuration and other technical conditions.

Final Thoughts

Separating the roles of a digital signature and a digital certificate makes it much easier to see the difference.

The main function of a digital certificate is to create an identity and associate that identity with a public key. A digital signature is a cryptographic technique for signing electronic information to help verify its authenticity and integrity.

So, they're not competing technologies. In many certificate-based workflows, they go hand in hand, the certificate provides a way to trust the public key, and the private key is used to create the digital signature.

Understanding this difference helps individuals and businesses make the right choice for signing and avoid confusing a simple signature image with a certificate-based digital signature. Never sign an important document until you have checked what type of signature is required by the recipient or the process to be followed.