What Is A Digital Signature And Why Do You Need It

Using a Digital Signature ensures that a message in transit is protected from intrusion or interception. A digitally signed document ensures the integrity of the message and that it was not altered in transit.

In this process, the server creates a digital signature by adding encryption to the content of the message. This encryption is a one-way hashing process, in which you will be using both your public and private keys. When you send a digitally signed document, your client can view the message, along with your electronic signature. In order to decrypt it, he uses your public key. With this, he can validate you and the authenticity of the message contents.

Digital signatures are used for many confidential messaging formats. Be it an email service, online financial transactions or photos watermarked with eBay ID, the process ensures that the content is protected. If the digital signature on the transmission is not the same as the public key of the digital certificate, the recipient can be sure that the message is altered.

How Does A Digital Signature Provide Confidentiality?

Basically, the server adds a digital signature to the message to be transmitted by using its key pair. This is known as Public Key Cryptography, the most commonly used process to deliver a digitally signed message. PKC (Public Key Cryptography) uses delivery systems based on Public Key Infrastructure.

How Public Key Infrastructure Works

PKI (Public Key Infrastructure) creates digital signatures using the public and private keys, which are unique to each user. The key pair is mathematically linked to each other. While the public key can be shared openly, the private key can only be used by the person who signs the transaction.

For each transaction, PKI generates a digital signature for the sender with his private key. During this process, a crypto code gets embedded into the message. When the electronically signed message arrives, the recipient can decrypt the digital signature with the sender’s public key. It validates the digital signature of the sender. This way, the recipient can be sure that the content of the document is not altered.

To illustrate a simpler example:

Consider A, who digitally signs a file by clicking ‘sign’ in his email app. The one-way hash process which we referred to earlier, calculates the hash value for the content of this file. A uses his private key or signing key to encrypt this hash value. Thus, he creates a digital signature, which gets embedded in the original message.

When A sends this file to B, his email app identifies the digital signature on the message. Now B can use A’s public key, which is openly available, to decrypt this digital signature. He can also calculate the hash value of A’s original file. In order to validate the sender, he compares this hash value with the decrypted hash from A’s message. If these two values are not the same, it means that the message was tampered with.

Why Do You Need A Digital Signature?

Many industries require a digital signature for business transactions. Most geographical regions have set their own standards for e-Signature processes that use digital signature technology.

These local e-Signature standards are based on PKI methodology. On an international level, these standards help prevent the chance of manipulations or forgery of electronically signed documents.

How To Create A Digital Signature?

If you want to create a digital signature, you can do it on your own by using a digital certificate. However, using self-signed certificates makes it difficult for your clients to validate your digital signature. Hence, the best way is to approach specific certificate authorities (CA) to obtain your digital signature. This lets the recipients easily verify your digital signature for authenticity.

First, you need to download a digital certificate from a trusted CA like GlobalSign or DocuSign. Install the certificate and then you can digitally sign your messages. By using ‘sign’ and ‘encrypt’ features on your email app, you can digitally sign and encrypt the messages to be sent to your clients. This is especially valued in the business circuits. Your clients are assured that the email is genuinely from you and not an impostor.

Not All Digital Signatures Are The Same

There are various types of digital signatures in use on different platforms. These document processing platforms allow the creation and use of different digital signatures. For example, Adobe PDF supports embedding details like an image of a physical signature, official seal, date, and location. Microsoft Word documents support visible and invisible digital signatures.

Types Of Digitally Signed PDF Documents

1. Certified: A certifying signature embedded in the PDF document protects it from being tampered. It also indicates that you sent the document. These PDF documents have a blue ribbon on the top, which is unique to each document. This contains the information about who signed it and who issued the certificate.
2. Approval: Approval signatures on the PDF document help to optimize your business organization’s approval procedure. Your approvals will be captured and embedded within the document.

Types Of Digitally Signed Word Documents

1. Visible: Single or multiple users can digitally sign the same Word document. The signatures will be displayed on the document similar to how you see them in a physical document.
2. Invisible: Invisible digital signatures keep your information hidden on the document. A visual blue ribbon is seen on the taskbar, which indicates the document’s authenticity and its origin.

Security Provided

Depending on the requirement, digital signatures provide security in the below three core services:

Authentication Of Sender- Proof of the signer of the document. Here digital signatures can identify the user.

Integrity Of Data- Proof of integrity of the content of the document. This proves that the data is not altered.

Non-repudiation- There is no chance for the sender to deny signing the document. If it is proved in court that the signer created the signature, he cannot falsely deny this fact.

Digital Signatures And Legal Enforcement

The digital signature process has been in use for many years. Many countries have set their own E-Signature standards and legislation. EU’s Directive for Electronic Signatures is in force since 1999, whereas the US has been implementing the Electronic Signatures in Global and National Commerce Act (ESIGN) since 2000. Many other countries have also adopted regulations similar to these two. This makes e-Signatures, digitally signed documents and contracts legally binding.