openssl spkac

SPKAC printing and generating utility 

openssl command


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 

specifies the input file name to read from or standard input if this option is not specified. Ignored if the -key option is used.

-out filename 

specifies the output file name to write to or standard output by default.

-key keyfile 

creates an SPKAC file using the private key in keyfile. The -in, -noout, -spksect, and -verify options are ignored if present.

-keyform PEM|DER|ENGINE 

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

-passin password 

specifies the input file password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in the openssl reference page.

-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.


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


outputs 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):



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 2000-2018 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 here: OpenSSL.


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PTC MKS Toolkit for Professional Developers 64-Bit Edition
PTC MKS Toolkit for Enterprise Developers
PTC MKS Toolkit for Enterprise Developers 64-Bit Edition


openssl ca

PTC MKS Toolkit 10.4 Documentation Build 39.