What Is A Client Certificate?

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A very ignorant question, sans doute.

I get my certificates from cacert.org, to whom I am very grateful. I follow what I take to be the official procedure, first creating .key and .csr on my server and then getting .crt by going to Server Certificate=>New at the cacert site.

I then place the key certficate *.key in /etc/pki/tls/private/
and what I call the client certificate *.crt in /etc/pki/tls/certs/ .

But I notice that there at www.cacert.org there is a Client Certificate folder as well as the Server Certificate folder, and it seems that one can create a “client certificate” there.

My quesion is: what is the purpose of this second client certificate?

And while I am on the topic, what are the recommended file permissions for PKI certificates?
I was a little surprised to find my .key has permission 640, while .crt has permission 644. The folder /etc/pki/tls/private/ on my server does not seem to have any special security;
it is owned by root but can be opened and listed by anybody. Is that the recommended setup?

2 thoughts on - What Is A Client Certificate?

  • In two words: some of the stuff you would only serve to clients that authenticate themselves. Well known way of authentication is:
    username/password. Client certificate serves the same purpose, it is just less known way of doing it.

    For secret key I usually have 400 (-r——-). For Certificate, it doesn’t matter that much: your server passes it over to anyone who requests it at the very beginning of SSL/TLS connection. I still keep it without write permission. You only change certificate/key once every year or two, so you don’t need write permission for these files in general…

    Note that if some daemon needs secret key and it is not designed to start as root (to read the key…) then drop privileges, then you will have to make secret key group readable, grant it to appropriate group, and make sure the poor daemon who can not start as root first is a member of that group.

    I hope, this helps.


    Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247

  • Am 24.10.2014 um 18:31 schrieb Valeri Galtsev :

    conceptional that means that the former is something that you known and the latter is something that you have (+ known), to authenticate yourself.

    and keep your key/cert-pair out of your system backups.