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PKI – The Backbone of Digital Signatures

PKI – The Backbone of Digital Signatures

Nidhi Prasad

PKI is a framework behind digital signatures that enables users to authenticate online signatures through robust, end-to-end encryption.

A digital signature is a PKI (Public Key Infrastructure) based online certificate that validates the signer’s authenticity, ensuring digital transactions are not forged or tampered with. E-signatures are precisely like traditional signatures in the sense that both are unique to the signer. However, e-signatures offer far more security and assurance concerning the document’s origin, identity, and integrity. Besides providing the highest standards of security, digital signatures are also legally binding, with numerous countries having their own set of laws and regulations legalizing digital signatures.

PKI - What does it mean?

PKI stands for Public Key Infrastructure, a system that allows users to create, store, and digitally exchange data using digital certificates. PKI enables users to sign documents online or offline without any fear of tampering or alteration.

Digital certificates fulfill a similar purpose, just like a driver’s license or a passport. They are used to secure the transfer of information, assert identity information, and verify the authenticity of messages through public-key cryptography. Likewise, a digital certificate allows businesses to encrypt, sign, and authenticate documents and contracts.

‘Infrastructure’ in PKI refers to the underlying framework used to encrypt information and validate digital signatures. It encapsulates various ‘pieces’ that make up the technology, including the software, hardware, procedures, and policies needed to create, manage, store, or withdraw digital certificates. In a PKI, Certificate Authorities (CAs) issue digital certificates that bind the public keys with the signer’s identity.

Components of PKI

There are three major components of PKI:

  • Digital certificates
  • Certificate authority
  • Registration authority

Digital Certificates

PKI functionality depends upon digital certificates - it is used as a form of electronic identification for various websites and organizations. These certificates are vital in securing connections between two communicating machines, helping identify and verify the credentials of the two parties.

Certificate Authority

A Certificate Authority (CA) issues certificates after validating users' digital identities, ranging from individuals and businesses to central servers. It is a body that allows organizations to verify themselves as public keyholders by issuing digital certificates. Devices rely on digital certificates issued by certificate authorities.

Registration Authority

A Registration Authority (RA) is responsible for receiving digital signing requests or renewals. The RA verifies these requests and forwards them to the Certificate Authority (CA). The CA will then use a certificate server to execute the request.

Also Read: Digital Signature Laws around the World

How does PKI work in Digital Signatures?

As we learned earlier, digital signatures use public key infrastructure (PKI) for digital identity authentication and end-to-end encryption. Therefore, it is essential to understand how PKI forms the backbone of digital signatures. PKI relies on two related keys, a public key and a private key. These two keys create a key pair (like a lock and key) to encrypt and decrypt a message using robust mathematical cryptography algorithms. The private key is used entirely for signing purposes, while the public key is used to verify signatures.

By using public and private code keys and providing the signatory with their digital fingerprint or identity, a digital signature is generated and encrypted using the signer’s private key. Here we will get to know how code keys work, taking Alice and John as an example:

  • Alice selects a file that needs to be digitally signed
  • Her computer calculates the unique hash or code value of the file content.
  • This hash value is encrypted with Alice’s private key to create her digital signature.
  • The original file, along with its digital signature, is then sent to John.
  • John uses a document application, which identifies that the file has been digitally signed.
  • The file is then decrypted using Alice’s private key.

What happens next in Digital Signatures?

Are they fully secure? Digital signatures carry online certificates which are used to verify that information is being transmitted and stored securely. However, it is important to note that security threats such as blocking private keys or exposing these keys through a system breach do exist. Thus it is vital to have digital certificates stored securely to avoid tampering or unauthorized access.

When sending out any document signed using a private key, the receiving party obtains the signer’s public key, allowing one to decrypt the document. The receiving party can view the unaltered document once it is decrypted.

Suppose the receiving party cannot decrypt the document using the public key. In that case, the receiver will get to know that the document has been altered or forged and that the signature doesn’t belong to the original signer. Again, it is all about trust, where the individual creating the signature must keep their private code key secret. If anyone has access to the signer’s private key, it could lead to forgery and signature tampering.

What happens if either the sender or receiver changes the document after it has been digitally signed? This can cause alterations in hash values in the document as the hash value for each file is unique. As a result, when the receiver compares the hash value to validate the data, the difference in the hash values would reveal that the file has been altered. Thus, the digital signature will appear altered or tampered with, and the verification will fail. Therefore, digital signatures are highly secure and one of the safest forms of authentication.


The process of creating a digital signature is simple and easy. With changing times and a rise in automation, signing documents digitally not only works out as a quicker option but also proves to be extremely convenient. Unlike manual, traditional signing processes, digital signatures bring added security to online transactions with PKI, making processes easier, safer, and quicker for businesses.

PKI keeps every component of the Internet secure, be it securely encrypting emails, signing documents online, securing retail transactions, encrypting or decrypting files, and more. PKI technology helps businesses meet the safety and protection requirements they need to secure transfer of information online.

Using PKI-powered solutions like DrySign, businesses can take their cybersecurity to the next level. Want to know more?


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