Key Manager Technical Features

Due to the different paths and use cases for encryption tools, key management solutions have likewise developed along varied paths, reflecting their respective origins. Many evolved from Hardware Security Managers (HSMs), some were built from the ground up, and others are offshoots from key managers developed for a single purpose, such as full disk or email encryption.

Most key managers include a common set of base features but there are broad differences in implementation, support for deployment scenarios, and additional features. The next few posts focus on technical features, followed by some on management features (such as user interface) before we conclude with the selection process.

Deployment options

There are three deployment options for enterprise key managers:

  • Hardware Appliance
  • Software
  • Virtual Appliance

Let’s spend a moment on the differences between these approaches.

Hardware Appliance

The first key managers were almost all appliances – most frequently offshoots of Hardware Security Modules (HSMs). HSMs are dedicated hardware tools for the management and implementation of multiple cryptographic operations, and are in wide use (especially in financial services), so key management was a natural evolution. Hardware appliances have two main advantages:

  • Specialized processors improve security and speed up cryptographic operations.
  • Physical hardening provides tamper resistance.

Some non-HSM-based key managers also started as hardware appliances, especially due to customer demand for physical hardening.

These advantages are still important for many use cases, but within the past five to ten years the market segment of users without hardening requirements has expanded and matured. Key management itself doesn’t necessarily require encryption acceleration or hardware chains of trust. Physical hardening is still important, but not mandatory in many use cases.


Enterprise key managers can also be deployed as software applications on your own hardware. This provides more flexibility in deployment options when you don’t need additional physical security or encryption acceleration. Running the software on commodity hardware may also be cheaper.

Aside from cost savings, key management deployed as software can offer more flexibility – such as multiple back-end database options, or the ability to upgrade hardware without having to replace the entire server.

Of course software running on commodity server hardware is less locked down than a secure hardware appliance, but – especially running on a dedicated properly configured server – it is more than sufficiently secure for many use cases.

Virtual Appliance

A virtual appliance is a pre-built virtual machine. It offers some deployment advantages from both hardware appliances and software.

Virtual appliances are pre-configured, so there is no need to install software components yourself. Their bundled operating systems are generally extremely locked down and tuned to support the key manager. Deployment is similar to a hardware appliance – you don’t need to build or secure a server yourself, but as a virtual machine you can deploy it as flexibly as software (assuming you have a suitable virtualization infrastructure).

This is a great option for distributed or cloud environments with an adequate virtual infrastructure.

That’s a taste of the various advantages and disadvantages, and we will come back to this choice again for the selection process.

Client access options

Whatever deployment model you choose, you need some way of getting the keys where they need to be, when they need to be there, for cryptographic operations. Remember, for this report we are always talking about using an external key manager, which means a key exchange is always required.

Clients (whatever needs the key) usually need support for the following core functions fo a complete key management lifecycle:

  • Key generation
  • Key exchange (gaining access to the key)
  • Additional key lifecycle functions, such as expiring or rotating a key

Depending on what you are doing, you will allow or disallow these functions under different circumstances. For example you might allow key exchange for a particular application, but not allow it any other management functions (such as generation and rotation).

Access is managed one of three ways, and many tools support more than one:

  • Software agent: A dedicated agent handles the client’s side of the key functions. These are generally designed for specific use cases – such as supporting native full disk encryption, specific backup software, various database platforms, and so on. Some agents may also perform cryptographic functions to additional hardening such as wiping the key from memory after each use.
  • Application Programming Interfaces: Many key managers are used to handle keys from custom applications. An API allows you to access key functions directly from application code. Keep in mind that APIs are not all created equal – they vary widely in platform support, programming languages supported, the simplicity or complexity of the API calls, and the functions accessible via the API.
  • Protocol & standards support: The key manager may support a combination of proprietary and open protocols. Various encryption tools support their own protocols for key management, and like a software agent, the key manager may include support – even if it is from a different vendor. Open protocols and standards are also emerging but not in wide use yet, and may be supported.

That’s it for today. The next post will dig into the rest of the core technical functions, including a look at the role of HSMs.