You can just start with one of the existing ones that have been validated such as GEMSOS [1] which is offered by AESEC [2] which was certified to TCSEC Class A1

You can just start with one of the existing ones that have been validated such as GEMSOS [1] which is offered by AESEC [2] which was certified to TCSEC Class A1 by the NSA according to the Orange Book standard or Integrity-178B which is offered by Green Hills Software which was validated against the SKPP of the Common Criteria [3] (the Common Criteria being the current preferred security standard framework used by most countries and validated against by basically every company). Being certified against the SKPP required a multi-month NSA penetration test with full source code and design specifications to discover zero deficiencies [4] so qualifies against the standard you are proposing. The certification was done at the behest of the DoD for the F-22 and the F-35, so you can be reasonably certain it was not a false certification by the NSA to make sure the premier fighter jets of the US are vulnerable. You can also look at some of the other certified systems linked here [5] though I am not sure which of them are still commercially viable or even functional on modern hardware. [1] https://www.nist.gov/system/files/documents/2016/09/15/aesec_rfi_mls-rtos.pdf https://www.nist.gov/system/files/documents/2016/09/15/aesec... [2] https://www.aesec.com/ https://www.aesec.com/ [3] https://www.commoncriteriaportal.org/files/epfiles/st_vid10362-vr.pdf https://www.commoncriteriaportal.org/files/epfiles/st_vid103... [4] https://www.commoncriteriaportal.org/files/ppfiles/pp_skpp_hr_v1.03.pdf https://www.commoncriteriaportal.org/files/ppfiles/pp_skpp_h... Page 116 [5] https://www.cse.psu.edu/~trj1/cse443-s12/docs/ch6.pdf https://www.cse.psu.edu/~trj1/cse443-s12/docs/ch6.pdf