spkac - SPKAC printing and generating utility
openssl spkac [-in filename] [-out filename] [-key keyfile] [-passin arg] [-challenge string] [-pubkey] [-spkac spkacname] [-spksect section] [-noout] [-verify] [-engine id]
The spkac command processes Netscape signed public key and challenge (SPKAC) files. It can print out their contents, verify the signature and produce its own SPKACs from a supplied private key.
Print out the contents of an SPKAC:
openssl spkac -in spkac.cnf
Verify the signature of an SPKAC:
openssl spkac -in spkac.cnf -noout -verify
Create an SPKAC using the challenge string ``hello'':
openssl spkac -key key.pem -challenge hello -out spkac.cnf
Example of an SPKAC, (long lines split up for clarity):
SPKAC=MIG5MGUwXDANBgkqhkiG9w0BAQEFAANLADBIAkEA1cCoq2Wa3Ixs47uI7F\ PVwHVIPDx5yso105Y6zpozam135a8R0CpoRvkkigIyXfcCjiVi5oWk+6FfPaD03u\ PFoQIDAQABFgVoZWxsbzANBgkqhkiG9w0BAQQFAANBAFpQtY/FojdwkJh1bEIYuc\ 2EeM2KHTWPEepWYeawvHD0gQ3DngSC75YCWnnDdq+NQ3F+X4deMx9AaEglZtULwV\ 4=
A created SPKAC with suitable DN components appended can be fed into the ca utility.
SPKACs are typically generated by Netscape when a form is submitted containing the KEYGEN tag as part of the certificate enrollment process.
The challenge string permits a primitive form of proof of possession of private key. By checking the SPKAC signature and a random challenge string some guarantee is given that the user knows the private key corresponding to the public key being certified. This is important in some applications. Without this it is possible for a previous SPKAC to be used in a ``replay attack''.