Decrypting PKCS#7 encrypted data in C#

Question

I am working on a solution that needs to decrypt PKCS#7 encrypted data, preferably in C#. As far as I can see, the .NET api has support for this through the System.Security.

Answer 1

The .NET framework has only rudimentary support for PKCS#7/CMS, so it does not support streaming the data.

You need a 3rd party library. As others have mentioned, BouncyCastle is an excellent choice. It does support PKCS#7 (PKCS#7 is also known as CMS).

Their tests are probably a good place to look for sample code: EnvelopedDataStreamTest.cs.