Cryptographic API (CryptoAPI) 是微软在 Windows 操作系统中添加的密码编译机能，作为数据加密与解密功能的重要基础，CryptoAPI 支持同步，异步的密钥加密处理，以及操作系统中的数字凭证 的管理工作。

目前的 CryptoAPI 支持下列工作：

由于 CryptoAPI 使用上过于复杂，因此微软另外为 CryptoAPI 开发更为容易使用的 CAPICOM 组件，以及 Data Protection API。

The Cryptographic Application Programming Interface (also known variously as CryptoAPI, Microsoft Cryptography API, MS-CAPI or simply CAPI) is an application programming interface included with Microsoft Windows operating systems that provides services to enable developers to secure Windows-based applications using cryptography. It is a set of dynamically linked libraries that provides an abstraction layer which isolates programmers from the code used to encrypt the data. The Crypto API was first introduced in Windows NT 4.0 and enhanced in subsequent versions.