Where does Keychain Access store Certificate files?

I want to submit a certificate request, but I don't want to create a new certificate开发者_如何学运维 (I already have one). Where is it stored because I want to upload that file.

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How about you export them as suggested in the link below?

http://www.utexas.edu/its/help/user-certs/804

1. In Keychain, select the certificate
2. Select File > Export