Local Area Networks (LANs) in Aircraft - FTP Directory Listing - FAA

should be emphasized that there is no right or wrong answer to the various question 24 topics,
because the individual answers are in terms of a specific context envisioned by the responder,
with no common context being provided for each respondent. Thus, whenever a respondent
answered “yes,” that person was thinking of a scenario in which that event could result in a
major fault. If they answered “no,” they did not think of such a scenario. There is a loose
correlation for those individuals whose corporate function was actively involved with making
software components that tended to answer “yes” more frequently to the question 24 A through
H than those individuals who worked for entities that were not actively creating aircraft
software.
Yes answers to questions 24F and 24G represent potential challenges to this study in that it has
been stated that confidentiality is not particularly relevant for safety. Nine respondents thought
that maintaining the confidentiality of passenger lists can have safety implications and 11
thought that revealing the current location of aircraft could have potential safety implications.
Should the FAA determine that confidentiality can have safety implications, then appropriate
confidentiality controls will need to be added to the exemplar airborne network architecture
recommended by this study.
Two different answers greatly surprised the authors of the survey:
• On question 17, it was expected to see many answers that aircraft software did not use
any operating system—which three of the five respondents did. From the point of view
of the study, this is a fine choice for the reasons discussed in section 4.4 of this report.
However, the authors were particularly pleased that one respondent is using “A
commercial operating system independently designed for high assurance uses (e.g.,
GreenHills Integrity Kernel).” From the point of view of this study, this is an
outstanding choice (see sections 4.3 and 4.4). On the other hand, another respondent is
also using “A general purpose commercial-off-the-shelf (COTS) operating system such
as MS-DOS, a Microsoft Windows variant (e.g., Windows XP), Mac OS, or a Unix
variant (e.g., Linux).” Section 4.3 of the study discusses why this choice is problematic.
• The above summary does not identify the relationships between a single respondent’s
answers. However, when that correlation is preserved, the respondents who are building
Level A software are doing so by constructing software components with more than 4000
lines of C/C++ code—indeed, one respondent stated that their Level A software has more
than 10,000 lines of C code. (Note: this does not count the lines of code for the
operating system, if any.) Software this large has many opportunities to have numerous
latent software bugs that attackers could leverage should that software be deployed in a
networked environment. This is a matter of significant concern.
B-6