What is MS-CAPI?

Microsoft Crypto-API and Microsoft Cryptographic Service Provider are components of the Microsoft operating system that enable devices, applications and certificates to communicate with each other.

• CSP: A CSP (CryptographicServiceProvider) implementation. This module implements the CryptoAPI calls defined by Microsoft. It is built and delivered as a .dll on Windows. CSP enables you to enhance applications and services in a Microsoft environment and their use with a smart card. There is no concept of a CSP on other platforms other than Microsoft Windows. 
• base CSP: Smart card vendors can write card minidrivers to present a consistent interface to their smart card type to the Microsoft Smart Card Base Cryptographic Service Provider (CSP) or Crypto Next Generation (CNG) Key Storage Provider (KSP) and to the Smart Card Management Interface. These card minidrivers plug in to Windows operating system code.

For smart card minidriver specifications pls visit the download page on Microsoft website.