At this time there is no way to enable and/or disable specific ciphers within the SSB (Syslog-ng Store Box).
An enhancement request has been raised with the One Identity SSB team for the inclusion of this feature within a future release.
Please review the list of Enhancement Requests published within the product release notes to determine if this specific Change Request is included in an upcoming release.
NOTE: Please see the "Configuring the Transport options for your Syslog type message source" section of the SSB Administration Guide for more information on choosing compatible vs strong ciphers for use within the SSB. While specific ciphers cannot be chosen, strong ciphers can be used to ensure stricter compliance.
For any further questions please contact the One Identity support team for further assistance.