SPKAC printing and generating utility


openssl spkac [-help] [-in filename] [-out filename] [-key keyfile] [-keyform PEM|DER|ENGINE] [-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 a usage message.

-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.


Whether the key format is PEM, DER, or an engine-backed key. The default is PEM.

-passin password

The input file password source. For more information about the format of arg see Pass Phrase Options 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.


Don't output the text version of the SPKAC (not used if an SPKAC is being created).


Output the public key of an SPKAC (not used if an SPKAC is being created).


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=MIG5MGUwXDANBgkqhkiG9w0BAQEFAANLADBIAkEA\ 1cCoq2Wa3Ixs47uI7FPVwHVIPDx5yso105Y6zpozam135a\ 8R0CpoRvkkigIyXfcCjiVi5oWk+6FfPaD03uPFoQIDAQAB\ FgVoZWxsbzANBgkqhkiG9w0BAQQFAANBAFpQtY/FojdwkJ\ h1bEIYuc2EeM2KHTWPEepWYeawvHD0gQ3DngSC75YCWnnD\ dq+NQ3F+X4deMx9AaEglZtULwV4=


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.


Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the License). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <>.


ca (1)

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