CAPICOM and CryptoAPI
[This sample code uses features that were implemented in MSXML 5.0 for Microsoft Office Applications. XML digital signatures are not supported in MXSML 6.0 and later.]
CAPICOM and CryptoAPI are frameworks supported by Microsoft to enable applications to offer cryptographic and other security-related services. CryptoAPI is C-based. CAPICOM is COM-based and can be used in scripting. For more information, see Cryptography under the Security section in the MSDN Library.