Google Chrome gives a lot of SSL information. Here is a screenshot:
Under "Key Usage", what does "Derive" mean?
It is not a Chrome popup; it is a MacOS X popup. Chrome delegates certificate management to the underlying OS. You get this popup only with Chrome on MacOS X (on Linux you will have the Gnome certificate viewer, on Windows the Windows certificate viewer).
The OS X certificate viewer shows the "Key Usages" which are defined in the "Key Usage extension" as specified in RFC 5280, section 188.8.131.52. This (optional) extension describe the usages for which the public key contained in the certificate may be used. OS X translates the combination of flags into a combination of "usage words" and there is not a 1-to-1 mapping. You get "Derive" when the
keyAgreement key usage is specified (which is normal for a SSL server certificate with a RSA key); to get "Encrypt", you need either the
dataEncipherment flag, or the combination of
keyEncipherment triggers "Wrap". You also get "Encrypt, Verify, Derive" if the key has type RSA and there is no Key Usage extension at all.