There was a thread on this not too long ago, Encryption problems with xp Thread #872528 Message #872528. How are you creating your object (are you dropping it on a form, or creating it programmatically)? If you have an object on the form, try setting the provider name through the properties window instead of through code, and see if that makes a difference. It looks like the provider name is needed when the class is created.

>I'v created a _cryptapi class using the _Crypt.VCX and set the .cprovidername.cprovidername="Microsoft Base Cryptographic Provider v1.0".
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>Calls to encrypt/decrypt using the new class work great on my development machine (W98), however the class chokes on an XP system. My research has shown that the "Microsoft Base Cryptographic Provider v1.0" has an image path of "rsabase.dll" in the registry. However on an XP machine, the same provider has an image path to "rsaenh.dll". It appears that rsabase.dll is not distributed with XP.
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>Since my application will be running across many platforms, I want to use a common CSP. My initial plan was just to use the same call and change the dll(image path) on my machine to point to rsaenh.dll for testing. Or I could create my own registry entry and specifically point to rsaenh.dll. However it appears that the underlying function(s) within rsaenh.dll are not the same because when I make the same call to rsaenh.dll, the object returns errors for invalid parameters.
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>Does anyone know of good documentation on the rsaenh.dll functions, or an updated version of _Crypt.vcx that will work with rsaenh.dll functions?
>Or maybe a "DUH", I'm just missing something?
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>Thanks,
>Greg Taylor