|-in filename||This specifies the input filename to read from or standard input if this option is not specified. Ignored if the -key option is used.|
|-out filename||specifies the output filename to write to or standard output by default.|
|-key keyfile||create an SPKAC file using the private key in keyfile. The -in, -noout, -spksect and -verify options are ignored if present.|
|-passin password||the input file password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).|
|-challenge string||specifies the challenge string if an SPKAC is being created.|
|-spkac spkacname||allows an alternative name form the variable containing the SPKAC. The default is SPKAC. This option affects both generated and input SPKAC files.|
|-spksect section||allows an alternative name form the section containing the SPKAC. The default is the default section.|
|-noout||dont output the text version of the SPKAC (not used if an SPKAC is being created).|
|-pubkey||output the public key of an SPKAC (not used if an SPKAC is being created).|
|-verify||verifies the digital signature on the supplied SPKAC.|
|-engine id||specifying an engine (by its unique id string) will cause spkac to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.|
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.