What is a Public Key Infrastructure (PKI)? 

Trust and security are fundamental pillars supporting online interactions. Without them, the integrity of online communications and transactions becomes compromised, leaving users vulnerable to identity fraud and cybercrimes. Public Key Infrastructure (PKI) provides a comprehensive framework that enables confidentiality, integrity, and authentication for digital interactions through cryptographic techniques.

What is a Public Key Infrastructure (PKI)?

Public Key Infrastructure (PKI) is a comprehensive system of technologies that enables and ensures the confidentiality, integrity, and authenticity of digital communications and transactions. It provides a framework for managing encryption, digital signatures, and authentication processes, enabling the establishment of trust among parties over public, unsecured networks like the Internet. Moreover, PKI establishes a secure communication channel using cryptographic keys and digital certificates.

Key Components of PKI

PKI relies on several key components working together to enable trusted digital identities and secure communications:

1. Digital Certificates: A digital certificate is a digital document that binds a public key to an entity (such as an individual, organization, or device). It is an electronic form of identification issued by a trusted third party known as a certificate authority (CA). The digital certificate contains information about the owner, the public key, the expiration date, and the CA’s digital signature to verify its authenticity.
2. Certificate Authority (CA): A CA is a trusted entity responsible for issuing, revoking, and managing digital certificates. It verifies the identity of certificate applicants before issuing certificates, thus establishing a chain of trust.
3. Registration Authority (RA): The RA assists the CA in the identity verification process. It collects and validates identity information from certificate applicants before passing it to the CA for certificate issuance.
4. Cryptographic key pairs: At its core, PKI utilizes asymmetric cryptography, which involves a pair of public and private keys.
5. Public Key: A public key is an openly shared and distributed cryptographic key. When sending a secure message, the recipient’s public key is used for encryption. Only the corresponding private key holder can decrypt and access the message. Public keys are mathematically linked to private keys, which are undisclosed.
6. Private Key: The private key is a secret key corresponding to a public key. The holder must keep it confidential and not divulge it. The private key decrypts messages encrypted with its corresponding public key and signs documents digitally. It’s essential to keep the private key secure. If someone else gets hold of it, they can pretend to be the key’s owner and access encrypted information or create fake signatures.

How Does PKI Work?

PKI processes bind public keys to the identities of different entities with a digital certificate. Digital certificate users undergo verification processes before receiving their certificates. After successful verification, the CA digitally signs and releases the public key tied to a specific user.

This procedure is done using the CA’s private key, thereby establishing the reliability of the user’s key through trust in the authenticity of the CA’s key. PKI operates on the foundation of encryption, transforming data into a secure format only the intended recipient can decipher through public and private keys.

PKI often works within a hierarchical structure. At the root of this hierarchy are the root certificate authorities (Root CAs). These highly trusted entities issue intermediate certificates to subordinate CAs, which, in turn, issue certificates to end entities like individuals, servers, or devices. This tiered structure enhances security and allows for scalability.

Maintaining PKI Integrity Through Certificate Revocation

Certificate revocation is crucial to the Public Key Infrastructure (PKI) framework. It involves declaring a digital certificate invalid before its scheduled expiration date. This is done to prevent the use of compromised, expired, or otherwise untrustworthy credentials, ensuring the security and integrity of the PKI ecosystem.

The CA that issued the digital certificate performs certificate revocation by producing a cryptographically authenticated statement of revocation. Certificate Revocation Lists (CRLs) and the Online Certificate Status Protocol (OCSP) provide information about the status of certificates—whether they are still valid or have been revoked.

The Role of Cryptography in PKI

Cryptography plays a central and foundational role in the functioning of Public Key Infrastructure (PKI). It provides the underlying principles and techniques that enable secure communication, data protection, identity verification, and trust establishment within the PKI framework. Here’s how cryptography contributes to PKI:

1. Encryption and decryption: Cryptography provides methods for encrypting and decrypting data, ensuring its confidentiality during transmission. With PKI, entities use cryptographic algorithms to encrypt sensitive information using the recipient’s public key.

Only the corresponding private key can decrypt this encrypted data. Encryption forms the backbone of PKI’s security mechanisms. By encrypting data during transmission, PKI prevents unauthorized parties from intercepting and accessing sensitive information.

2. Integrity and Authentication through Digital Signatures: Digital signatures use cryptographic techniques to provide integrity and authentication for digital documents, messages, or transactions. When a sender signs a document using their private key, the recipient can verify the signature using the sender’s public key. If the document has been altered in any way, the signature verification will fail, indicating that the document’s integrity has been compromised.

Similarly, the recipient can confirm the authenticity of the sender’s identity by verifying the digital signature with the sender’s public key, ensuring that the claimed sender truly sent the document.

3. Certificate Signing and Verification: Certificates, which are issued by Certificate Authorities (CAs) use cryptographic techniques to bind an entity’s identity to its public key. CAs use their private keys to sign these certificates, ensuring their authenticity and integrity. Consequently, recipients can verify the CA’s signature using the CA’s public key to trust the certificate’s validity.

Use Cases and Applications of PKI

Public key infrastructure provides the fundamental technology to enable trusted digital identities and secure communications for a vast array of critical applications and use cases, including:

1. Secure Web Browsing (HTTPS)

Secure web browsing is one of the most common and visible PKI applications PKI enables the implementation of HTTPS, which ensures encrypted communication between a user’s browser and a website’s server. SSL/TLS certificates, a form of digital certificate, are used to verify the identity of the website and encrypt data exchanged between the user and the server.

2. Email Security

PKI enhances email security by enabling encryption and digital signatures. Encrypted emails ensure that only the intended recipient can read the content, while digital signatures verify the sender’s identity and message integrity.

3. Virtual Private Networks (VPNs)

PKI is integral to establishing secure connections in VPNs. PKI allows users and devices to authenticate each other, ensuring that only authorized users can access the network and all communication remains encrypted.

4. Code and Software Signing

PKI is crucial in code and software signing.

5. IoT Security

In the Internet of Things (IoT) landscape, PKI provides a way to secure device communication and authentication. Devices can use digital certificates to authenticate themselves to each other, enhancing overall IoT security.

6. Document and Data Encryption

Beyond email, PKI encrypts various types of data, such as files and databases. This ensures that even if unauthorized individuals gain access to the data, they cannot decipher its contents without the appropriate decryption key.

7. Secure Online Transactions

In e-commerce and online banking, PKI ensures secure online transactions by establishing trust between customers and businesses. SSL certificates indicate that the website is authentic and encrypts financial transactions.

Challenges of PKI 

Trusting Certificate Authorities (CAs) is central to PKI. If someone compromises a CA or if it issues fraudulent certificates, they undermine the entire security and trustworthiness of the PKI.

Key management is crucial for both CAs and digital certificate holders. When private keys are compromised, attackers can decrypt intercepted communications by impersonating the key owner. The implications are worse if the private keys of CAs get into the wrong hands; an attacker can issue forged certificates with the private key of a compromised CA.

Decentralized PKI

Decentralized Public Key Infrastructure (PKI) is an evolving concept that aims to address some of the challenges and limitations of traditional PKI systems. However, traditional PKI relies on centralized Certificate Authorities (CAs) to issue and manage digital certificates.

On the other hand, decentralized PKI, the network of nodes distributes trust, which reduces dependence on a single trust point and strengthens the system against single points of failure or compromise. Furthermore, it leverages blockchain technology, distributed ledgers, and cryptographic principles to achieve its goals.

Conclusion

Public Key Infrastructure is a foundational technology that empowers secure digital communication, authentication, and data protection. Its role in safeguarding our digital interactions and transactions is indispensable, as it underpins many aspects of modern cybersecurity.

Identity.com

In the digital age, identity verification is crucial to combating identity theft and mitigating against unauthorized access. As an identity-focused blockchain company, we create solutions built on blockchain that will reduce such occurrences. This is one of the reasons we embrace blockchain. As a company, we develop and build identity management systems that focus on keeping users’ privacy private and with strong security, making identity verification a more formidable process.

We contribute to a more user-centric future via identity management systems and protocols. We also belong to the World Wide Web Consortium (W3C), the standards body for the World Wide Web. Identity.com‘s work as a future-oriented company is helping many businesses by giving their customers a hassle-free identity verification process. Identity.com is an open-source ecosystem providing access to on-chain and secure identity verification. Our solutions improve the user experience and reduce onboarding friction through reusable and interoperable gateway passes. Please get in touch for more information about how we can help you with identity verification and general KYC processes.