Public Key Infrastructure (PKI) is a governance layer that helps organizations manage the locks and keys to their enterprise data and resources. This includes issuing and revoking certificates, encryption, and authentication.
One commonly misunderstood aspect about PKI is asymmetric cryptography. This is an encryption method that uses public and private keys to validate authorized access to a resource. In this article, we’ll review public key vs private key differences, how they work together, and PKI best practices.
This encryption technique improves digital trust, deters breaches, and supports a better overall security posture.
Public key vs private key differences
In asymmetric cryptography, data is encrypted using paired public and private keys. The keys work together to encrypt and decrypt data securely.
Public key
Public keys do not contain secret details or vital information. They:
- Are openly shared: They can be distributed broadly without compromising security.
- Encrypt and verify: They can be used to encrypt data or verify a digital signature.
For example, a server’s SSL/TLS certificate contains its public key, which can be used to encrypt data that can only be decrypted by the correct private key. When looking at public key vs private key uses, public keys function somewhat like locks. You can also think of them as email addresses with specific instructions for how to return a message (encryption).
Private key
Private keys should never be public because their function is to decrypt data that has been “locked” by the corresponding public key. They must remain secret and tightly controlled in your organization. Private keys:
- Decrypt: They can be used to decrypt data encrypted with the corresponding public key.
- Sign: Private keys can create a digital signature proving the origin of the data or application.
If the private key is compromised, attackers can impersonate systems, decrypt sensitive data, or sign malicious software. When looking at public key vs private key uses, private keys function simply like keys.
How they work together
Public and private keys work together to encrypt and authenticate data across your organization. For example:
- Encryption: A client encrypts a session key with the server’s public key, and only the server’s private key can decrypt it.
- Decryption: A digital signature created with a private key is validated by others using the public key.
This public key vs private key dynamic makes it possible to prove both identity and confidentiality at scale. A simple use case could be:
- A client tries to gain access to resources on a server.
- The client uses their private key to create a digital signature, then uses the server’s public key to encrypt the request.
- The client submits the request.
- The server receives the request and uses its private key to decrypt the request, then uses the client’s public key to authenticate who sent the request.
Automated key management is essential
Keys and certificates protect everything that could be included in your organization’s architecture, from websites and VPNs to IoT devices and cloud workloads. Therefore, key management is vital across your business. A misplaced key or expired certificate could have far-reaching consequences, some of which can’t be seen until years down the line.
However, failure to properly manage keys could lead to outages, failed audits, and breaches.
- Outages: Expired certificates disrupt services, leading to downtime for employees and customers.
- Audit failures: Gaps in key handling can lead to compliance penalties.
- Security incidents: Stolen or misused private keys enable impersonation and data breaches.
The main key management challenge is, simply, scale. Certificates can number in the millions, making manual oversight impossible. The public key vs private key dynamic helps your organization protect and validate data, but only if keys are handled properly. They should never be stored in plain text files; preferably, you would have hardware security modules (HSMs) or vaults for keys.
The role of PKI in governing keys
PKI offers a framework for tying public and private keys to trusted identities via digital certificates. Its core functions include:
- Certificate Authorities (CAs): Issue certificates and vouch for the authenticity of entities.
- Certificate revocation lists (CRLs) and OCSP: Support the invalidation of compromised keys.
Without PKI, the public key vs private key dynamic would lack trust, as anyone could claim an identity without verification. Enterprises rely on PKI for:
- Web servers and SSL/TLS encryption
- Authentication of users and devices
- Securing DevOps pipelines and cloud workloads
- Protecting IoT ecosystems
Business impacts of key mismanagement and best practices
If your organization’s PKI does not have solid processes and protections, your organization could face key mismanagement risks like outages, incidents, or compliance issues.
Service outages + lifecycle automation
Expired or misconfigured certificates can cause outages and employee downtime. Every minute of unplanned downtime risks your business money and productivity.
Best practice: Implement certificate lifecycle automation, automatically renewing and provisioning certificates before expiration.
Compliance failures + policy enforcement
Failed audits from unmanaged or misused keys could lead to fines, penalties, and/or reputational damage. Regulations like PCI DSS require you to show control over certificates in your organization, which is difficult to prove if your key management policies and capabilities are lacking.
Best practice: Enforce PKI policies and maintain auditable logs of every key lifecycle event. This ensures that when a regulatory body needs information to perform an audit, you have it at the ready.
Security incidents (key theft/misuse) + private key protection
Lost or stolen private keys allow attackers to impersonate trusted systems or sign malicious code. In Microsoft’s Azure Key Incident in 2021 (disclosed June 2023), a key was accidentally included in a crash dump, found by attackers, and used to bypass Microsoft’s authentication systems to gain unauthorized access to Microsoft 365 services.
Best practice: Store private keys in HSMs or vaults, enforce role-based access controls, and require on-device key generation where possible.
Operational burden + centralized visibility and inventory
Teams spend hours tracking certificates with spreadsheets or siloed tools. Most organizations don’t know how many certificates they have or what stage of the lifecycle those certificates are in.
Best practice: Implement continuous discovery and centralized inventory across all environments (cloud, on-prem, DevOps) to eliminate blind spots.
Reputational damage + crypto-agility
Outages, breaches, and weak cryptography erode customer trust and brand value, negatively impacting your organization’s reputation. If your customers cannot trust that their personal data will be safe in your organization’s hands (or, worse, if they become victims of fraud due to a breach), they become much less likely to remain your customers.
Best practice: Build crypto-agility into your organization’s PKI and key management processes. This means standardizing on strong/approved algorithms, planning for rapid re-issuance at scale, and preparing for a period of incoming change.
How to prepare for the future of cryptography
Cryptography is evolving rapidly, and organizations need to prepare to stay ahead of threats. Technologies are evolving quickly with new rules happening now and some requirements are expected within the next few years including:
- Shorter certificate lifespans: TLS certificates currently expire after 398 days. Within the next decade, the expiry time will be 47 days. This means your organization will need to be able to refresh certificates much more often as their lifespan drops almost 90%.
- Post-quantum cryptography (PQC): Quantum computers will one day undermine today’s public vs private key algorithms. They will be able to brute-force break current encryption standards, your organization must continually improve PKI and key management processes to defend against attacks using quantum technologies.
- Integration with DevOps/Cloud: PKI must align with modern infrastructure—APIs, containers, and CI/CD pipelines. Integrations with AI tools must also be carefully implemented and secured with strong certificates.
- Strategic priority: Organizations moving toward automation and agility minimize risk and enable innovation. Unless your organization is extremely high-risk for data breaches and other security incidents (government, health, and payments, among others), small, steady improvements over time will be more manageable for security teams and keep your organization safe in the long run.
Eliminate outages, reduce audit risk, and give your team back valuable time with end-to-end certificate lifecycle automation. From discovery to renewal to post-quantum readiness, Keyfactor Command makes PKI scalable, visible, and reliable—everywhere your business runs.
