What Is a Public Key Infrastructure (PKI)? 

Key Takeaways:

• Public Key Infrastructure (PKI) is a foundational system for ensuring the confidentiality, integrity, and authenticity of digital interactions using cryptographic techniques.
• PKI’s core components include digital certificates, Certificate Authorities (CAs), Registration Authorities (RAs), and cryptographic key pairs (public and private keys).
• PKI operates by binding public keys to entity identities via digital certificates, ensuring secure communication on public networks.
• Maintaining PKI integrity involves certificate revocation to prevent the use of compromised or untrustworthy credentials.
• Decentralized PKI, leveraging blockchain technology, addresses traditional PKI limitations by distributing trust and enhancing system security against failures.

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)?

Key Components of Public Key Infrastructure (PKI)

PKI relies on a set of crucial components that collaborate 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 serves as 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 assesses the identity of certificate applicants before issuing certificates, hence establishing a chain of trust.
3. Registration Authority (RA): The RA aids the CA in the identity verification procedure. It gathers and validates identity information from certificate applicants before forwarding 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 employed for encryption. Only the matching private key holder can decrypt and access the message. Public keys are mathematically connected to private keys, which remain undisclosed.
6. Private Key: The private key is a secret key associated with a public key. The holder must maintain it confidential and not disclose it. The private key decrypts messages encrypted with its corresponding public key and signs documents digitally. It’s crucial to keep the private key secure. If someone else acquires it, they can impersonate the key’s owner and access encrypted information or create fake signatures.

How Public Key Infrastructure (PKI) Functions

PKI binds public keys to the identities of various entities through digital certificates. Before receiving certificates, users undergo stringent verification processes. After successful verification, the CA digitally signs and releases the public key, ensuring its reliability through trust in the CA’s authenticity. PKI relies on encryption to transform data into a secure format that only the intended recipient can decipher using their public and private keys.

PKI often operates within a hierarchical structure, with highly trusted Root Certificate Authorities (Root CAs) at the top. These Root CAs issue intermediate certificates to subordinate CAs, which, in turn, issue certificates to end entities. This tiered approach enhances security and 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.

Applications of Public Key Infrastructure (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 applications of PKI. PKI enables the implementation of HTTPS, ensuring encrypted communication between a user’s browser and a website’s server. SSL/TLS certificates, a type of digital certificate, are used to verify the website’s identity and encrypt data exchanged between the user and the server.

2. Email Security

PKI enhances email security by enabling encryption and digital signatures. Encryption ensures that only the intended recipient can read the email content, while digital signatures verify the sender’s identity and the message’s 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. For instance, developers sign their software with digital signatures to indicate that no one has tampered with it and that it comes from a trusted source. This ensures software integrity and helps users avoid downloading malicious code.

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

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.