Microsoft software imports client certificates from .p12 (also known as .pfx) files. If you received .crt and .key files instead of a .p12 file, you must convert them to .p12 format. You can do this with the free program OpenSSL.exe from the OpenSSL Project.

Example

You receive the files fred.crt and fred.key . To convert them to a single fred.p12 file, use the following command:

openssl pkcs12 -inkey fred.key -in fred.crt -export -out fred.p12

This command prompts for the password to the fred.key file before it writes the fred.p12 file.