I'm aware that sites like StartSSL use Client-Certificates, I opened mine in Firefox and it showed me: "SSL-Client-Certificate", "E-Mail-Receiver-Certificate", "E-Mail-Signer-Certificate".

Now I'm asking myself, for self-signed certificates, is it possible to restrict usage of X.509(v3?) certificates to be only TLS-Client? (-> no server / no S/MIME)

1 Answer 1


Yes, it is possible for X.509 to be only "TLS client" (actually to have the extended key usage only set to client). I suggest you to take a look at XCA, it is free a graphical tool which will allow to easily create and manage certificates (it is actually a small PKI).

You will then be able to visually see all the main options a certificate can have, which one fits in the client or server template profiles, and play with these options.

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