Import Key File Dialog Box
When you select an existing key file to sign the assembly, this dialog box prompts you to enter the correct password for the key file. Entering the password imports the key file into the local cryptographic database store for use in the current project.
This option supports only Personal Information Exchange (.pfx) files. After you import the key file into the project, you can change the password using Change Password; the new password must be at least 6 characters in length.
To access the ImportPFXKeyDialog dialog box, on the Signing page, click Sign the assembly; then in the Choose a strong name key file drop-down list, select <Browse...>.
The ImportPFXKeyDialog dialog box also appears when you open an existing project in which the assembly or the manifests have been previously signed, but the key files are not in your personal key-container list or your personal certificate store.