The Utimaco CryptoServer is a general-purpose _Hardware Security Module_ (HSM) provided by Utimaco. An HSM is a PCIe-based computing environment -- CPU, memory, storage etc -- with both physical and logical protections that are designed to provide the computing environment with an awareness of its physical surroundings and state. The circuits are what allow the HSM to protect the keys and other secrets that it stores.
Attempts to defeat the physical protections/anti-tamper circuits results in the complete erasure of any stored secrets, sensitive material, etc.
Logical access to the CryptoServer is supported by host libraries that implement both a proprietary cryptosystem (CXI) and several standards'-based cryptosystems (CSP/CNG, PKCS#11, etc), as well as provide the communications protocols, drivers and so on, which are necessary to reach the device.
The current version of the physical hardware is sold as CryptoServer, and the supporting software libraries, tools and documentation (on the host and on the CryptoServer) is sold as the Utimaco SecurityServer.
For information on supported Application Programming Interfaces (APIs), please see the relevant documentation in the installation, at <install>\Documentation\Crypto_APIs\*.
What these host APIs all have in common is an understanding of current, 'modern' generic cryptographic operations, algorithms, mechanisms, etc. Because cryptographic tools are continually being developed or improved, the capabilities of the cryptosystems as shipped may not include awareness of these future mechanisms, or may not be able to provide these new concepts in cryptography. This is currently the issue with those algorithms that are targeting the Post-Quantum Computing era.
For this reason, Utimaco SecurityServer also provides several Software Development Kits (SDKs).
Utimaco use of API and SDK: Software that is developed on the host uses one or more "APIs". Software that is developed to run on the CryptoServer is developed using an "SDK". An API is always used by host-side application code, and the SDK is always used to develop custom, embedded (HSM) firmware.