CAPICOM is a discontinued ActiveX

ActiveX

ActiveX is a framework for defining reusable software components in a programming language-independent way. Software applications can then be composed from one or more of these components in order to provide their functionality....

 control created by Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 to help expose a select set of Microsoft Cryptographic Application Programming Interface

Cryptographic Application Programming Interface

The Cryptographic Application Programming Interface is an application programming interface included with Microsoft Windows operating systems that provides services to enable developers to secure Windows-based applications using cryptography...

 (CryptoAPI) functions through Microsoft Component Object Model

Component Object Model

Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...

 (COM). It was intended to enable every environment that supports ActiveX to use Microsoft Cryptographic technologies, including web pages that are opened with Microsoft Internet Explorer

Internet Explorer

Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...

 or any other web browser that supports ActiveX.

CAPICOM can be used to digitally sign data, inspect, verify and display their digital signature and/or digital certificate, add or remove certificates to or from the certificate stores, and finally, to encrypt or decrypt data.

CAPICOM Version 2.1.0.2, the latest and last version of CAPICOM, is officially supported on Windows Vista. However, Microsoft has announced that CAPICOM is discontinued and is no longer being developed. Microsoft suggests replacing CAPICOM with .NET Framework

.NET Framework

The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...

's X509 Cryptographic Classes and a number of other alternatives.