Keyless Signature Infrastructure Provider (rsyslog-ksi-ls12)

Module Name: rsyslog-ksi-ls12

Available Since: 8.27

Author: Guardtime & Adiscon


The rsyslog-ksi-ls12 module enables record level log signing with Guardtime KSI blockchain. KSI keyless signatures provide long-term log integrity and prove the time of log records cryptographically using independent verification.

Main features of the rsyslog-ksi-ls12 module are:

  • Automated online signing of file output log.
  • Efficient block-based signing with record-level verification.
  • Log records removal detection.

For best results use the rsyslog-ksi-ls12 module together with Guardtime logksi tool, which will become handy in:

  • Signing recovery.
  • Extension of KSI signatures inside the log signature file.
  • Verification of the log using log signatures.
  • Extraction of record-level signatures.
  • Integration of log signature files (necessary when signing in async mode).

Getting Started

To get started with log signing:

Currently the log signing is only supported by the file output module, thus the action type must be omfile. To activate signing, add the following parameters to the action of interest in your rsyslog configuration file:

Mandatory parameters (no default value defined):

Note: parameter names are case-insensitive.

  • sig.provider specifies the signature provider; in case of rsyslog-ksi-ls12 package this is "ksi_ls12".
  • sig.block.levelLimit defines the maximum level of the root of the local aggregation tree per one block.
  • sig.aggregator.url defines the endpoint of the KSI signing service in KSI Gateway. Supported URI schemes are:
    • http://
    • ksi+http://
    • ksi+tcp://
  • sig.aggregator.user specifies the login name for the KSI signing service.
  • sig.aggregator.key specifies the key for the login name.

Optional parameters (if not defined, default value is used):

Note: parameter names are case-insensitive.

  • sig.syncmode defines the signing mode: "sync" (default) or "async".
  • sig.hashFunction defines the hash function to be used for hashing, default is "SHA2-256". Other SHA-2, as well as RIPEMED-160 functions are supported.
  • sig.block.timeLimit defines the maximum duration of one block in seconds. Default value "0" indicates that no time limit is set.
  • sig.keepTreeHashes turns on/off the storing of the hashes that were used as leaves for building the Merkle tree, default is "off".
  • sig.keepRecordHashes turns on/off the storing of the hashes of the log records, default is "on".

The log signature file, which stores the KSI signatures and information about the signed blocks, appears in the same directory as the log file itself; it is named <logfile>.logsig.


To sign the logs in /var/log/secure with KSI:

# The authpriv file has restricted access and is signed with KSI
authpriv.*    action(type="omfile" file="/var/log/secure"

Note that all parameter values must be between quotation marks!

See Also

To better understand the log signing mechanism and the module’s possibilities it is advised to consult with:

Access for both of these documents requires Guardtime tryout service credentials, available from