“Keyset does not exist” when using SignData function with RSA

“Keyset does not exist” when using SignData function with RSA

"Keyset does not exist". I know that there are tons of question about this error, but mine is totally different.

I'm not gona use the key from windows certificate store, but load the public key & private key from 2 bare strings, using method "fromXMLString".

rsa.fromXMLString "<RSAKeyValue><Modulus>......"

then

rsa.SignData buffer, algSHA1

and Booom! : "Keyset does not exist"

Can someone please tell me that using the rsa key pair from 2 xmlStrings is innocent and it entirely does not relate to windows certificate store? I have my own approach of storing & loading certificate/keys.

PS: The other answers for questions on this error told questioner to set correct permission for private key in cert-store. But in my case, I used no private key file in that store, right ?