I need a certificate to exchange a data with some service provider. This provider suggests to use OpenSSL, they provide example for every step to create a certificate:
- Create new private key.
- Create certificate request (CSR) based on the private key from Step 1.
- Send them CSR and upon receiving new certificate, merge it with a key from Step 1.
- Use certificate with key to sign a data.
I tried to replicate these steps with Microsoft CA:
- In the Certificates snap-in I created manual certificate request (*.req that I believe is the same as *.csr). There were no options to indicate which key to use
- I sent them request and successfully received certificate without key
- When imported this received certificate into my Personal store, a key was added automatically (to my surprise) but I have no idea what was that key.
- Now I can export this certificate with a key (*.pfx) and able to sign the data. However, service providers reports error ("signed by unknown certificate").
The question is: what was a key used to create CSR? What was a key that was merged? Where is error in my steps?