My goal is to write a custom CNG CSP, I encounter the problem with the sample provider from the CNG development kit, but it already exist with Windows' native default CNG provider. I have a Server 2008 CA issuing certificates to client running Win7. Some clients use outlook 2010 and they can sign their messages, other use outlook 2003 and when trying to sign mail receive "an error occurred in the underlying security system" I already verified that the template used for issuing the certificates, although using a CNG provider, uses RSA with SHA1 signature and not any new algorithms, not sure if this is related. Thanks,

Outlook 2003 does not support CNG providers. Only Outlook 2007 and Outlook 2010 support CNG providers (even if they are only using RSA and SHA1). This is expected behavior. Brian

Hi, Agree with Brain that Outlook 2003 does not support CNG providers. For more information, please refer to: Cryptography Next Generation http://technet.microsoft.com/en-us/library/cc730763(WS.10).aspx Hope it helps. Regards, BruceThis posting is provided "AS IS" with no warranties, and confers no rights. Please remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.