Strong Name sn.exe: Failed to install key pair — Object already exists

Question

I have 2 different versions of the same project on my machine. One from the code trunk, and the other from a code branch. These projects use a .pfx key to enable strong naming.

Answer 1

We had the same problem after doing a "refresh" on Windows 10. Here's what worked for us:

1. Start a command prompt as administrator.
2. Run "sn -m n" to make certificates user-based rather than machine-based.
3. Install the certificate as normal (either "sn -i VS_KEY_XX" or using the "properties" dialog in VS).

It was like the refresh stored the old containers in some hidden area, where they couldn't be deleted (but also interfered with the addition of the same container). Changing to user-based allows a clean slate from the current user's perspective. Note that if you have multiple users on the same machine, they would probably each need to register the certificates.

Answer 2

I have managed to resolve my issue, without fully understanding the cause. I found a post about a similar issue here, but did not fit my circumstance precisely, as I had only ever logged on to my machine as a single user.

The post showed how to delete the container, but I couldn't do this either as it said the container didn't exist. What it did though was prompt me to run the command prompt as an Administrator, which I had not done previously. This allowed me to uninstall and re-install the certificate, and both versions of the project now build successfully.

My assumption is that somehow the certificate had initially been installed (by me) under a different user than the one I tried to install with the second time, though I don't know why this would be, as I have only ever logged on to the machine as a single user. It remains something of a mystery to me.

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Summary:

1. Start the developer command prompt as administrator, otherwise you'll get a misleading error saying the container doesn't exist.
2. Run sn -d VS_KEY_XXXXXXXXXXX to remove the old key.
3. You should now be able to reinstall the certificate.