Is my computer compromised if I see unknown certificate in my login Keychain?

Dear Administrator,

I opened Keychain Access.app and find the following completely unknown Certificates in my login Keychain.

DoD Email CA-29

DoD Root CA 2

KANG.WEI.1231244561

KANG.WEI.1231244561

The rest of the certificates are familiar to me. Does this mean that my computer had been compromised? or what does this mean? I have no relation to Department of Defense, and Wei Kang is the name of two different persons I knew in my life. How come these certificates are in my Keychain?

Sincerely yours,

Zigang Pan

Ph.D.

Tel: ******

Fax: ********

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