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

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exposes previously isolated computational systems to new classes of failures resulting from both accidental as well as intentionally malicious attacks that could affect safety of flight. Section 7 has suggested specific extensions that are needed to extend current FAA policy to address the additional threats and issues that occur in networked airborne environments. Sections 10.1 and 10.3 directly address the adequacy of existing regulations. Because this topic was a central element of phase 2, the more complete response to this topic occurs in section 10, with this section primarily being an initial description. 9.9 GROUND-TO-AIR COMMUNICATION. This report recommends that the signals in space (e.g., radio or satellite communications) used for ground-to-air communications must use transport security cover (i.e., encryption of the wireless signal in space occurring at the OSI physical layer). This hinders nonauthorized entities from eavesdropping upon these communications and discourages attempts to potentially inject false communication signals into the data stream (e.g., possible man-in-the-middle attacks). However, these links will remain potentially vulnerable to availability attacks caused by hostile jamming unless mitigation techniques such as AJ waveforms or LPI/LPD waveforms are used. 9.10 WHAT IS THE EFFICACY OF CYCLIC REDUNDANCY CHECKS WITH RESPECT TO SECURITY? Software parts are currently assured, in many cases, by having a 32-bit polynomial cyclic redundancy check (CRC) wrapped around each part packaged with other identifying information (aircraft type/serial, system part numbers, software part number, etc.) and then that package is wrapped within another CRC. This helps to ensure not only nontampering (internal CRC) but also error-free transmission of the software part and the entire data package (wrapping CRC). This approach has semantically overloaded the CRC concept to handle two different purposes: • Polynomial codes (CRCs) are mechanisms commonly used within data communications to detect and fix transmission bit errors. Industry uses different polynomial coding techniques in different environments to address specific network requirements. The wrapping CRC function of the previous paragraph corresponds well with this use case. • The internal CRC is intended to provide identity and integrity protections for received software parts. This study states that it is entirely appropriate to use CRCs as polynomial codes to assist in transmission bit error detection and correction. This is, after all, the historic reason for which CRC technology was created. However, this study states that it is inappropriate and risky (potentially dangerous) to use internal CRCs to provide identity and integrity protections (i.e., the inner CRC) within networked environments. The United States and world standard mechanism by which the latter technique is securely accomplished is by code signing in conformance with the U.S. Federal 130
DSS (FIPS 186 [81]). Code signing is widely used by both government and industry (e.g., Java code signing). FIPS 186 was discussed in section 6.1.1 (see figures 24 and 25). FIPS 186 has significant security advantages when compared to CRCs: • FIPS 186 provides a high-assurance mechanism to establish identities. In most implementations, these identities are assured and certified by a highly trusted subject (i.e., the CA). Also, if the identity is subsequently modified after signing, that modification will be detected by the FIPS 186 verification process. By contrast, the identities of the CRC approach are not verified by a trusted third party or by any other mechanism (i.e., there is no mechanism to verify that the identity is what it claims to be) nor is there a mechanism to discern whether the identity was changed (modified) or not over time. • FIPS 186 provides a superior approach to integrity protection when compared to CRCs. When CRCs are used for integrity, information (e.g., software, identities) can be modified and CRCs can be recomputed during man-in-the-middle attacks by the attacker in such a way that the received software parts can still pass the CRC checks. However, any attempt to alter FIPS 186 message digests (one-way hashes) will be detected during the FIPS 186 verification process (see figure 25). Thus, the integrity protection of all signed information, including both code and identity information, is trustworthy when using FIPS 186. However, the integrity of the CRC approach is questionable. • FIPS 186 provides a mechanism to authenticate the established identity of the signer (if required) using a highly assured authentication mechanism based on PKI technology. • FIPS 186 provides very strong nonrepudiation assurances, but CRCs do not have any nonrepudiation attributes. 10. ANSWERS TO THE PHASE 2 QUESTIONS. This section discusses several certification concerns that were identified during the original FAA Screening Information Request for this study. These specific questions formed a starting point for the work performed in phase 2 of this study. The exemplar architecture presented in section 8.3 describes the generic airborne network environment that identifies how many of these specific questions should be answered. 10.1 ARE CURRENT REGULATIONS ADEQUATE TO ADDRESS SECURITY CONCERN? The current regulations need to be extended to address network risks. Networks have very different attributes than the complex systems that the FAA has addressed to date. Section 7 identified specific changes needed to extend DO-178B and ARP 4754. However, other FAA regulations also need to become similarly enhanced. For example: 131
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DOT/FAA/AR-08/31 Air Traffic Organi
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1. Report No. DOT/FAA/AR-08/31 4. T
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5.4.2 Aircraft as a Node (MIP and M
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11.1 Findings and Recommendations 1
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22 Customer’s L3VPN Protocol Stac
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LIST OF ACRONYMS AND ABBREVIATIONS
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PBN PC PE PEP PFS PIB PIM-DM PIM-SM
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This report states that the primary
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1. INTRODUCTION. This is the final
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protocol (IP)-based communications.
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of linking aircraft-resident system
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Industry and governments are extrem
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2.1 NOTIONAL NETWORKED AIRCRAFT ARC
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Other Control Sites Controller ATC
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• The security viability of curre
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alternative requires that parallel
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Aircraft network security is a syst
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4. NETWORK RISKS. This section spec
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General Threat Identifiers FAILURE
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esources so that the required real-
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“With the rise of client-side att
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• During an 11-month period (Apri
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attempt the theft of passwords. Non
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IP networks are organized in terms
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either the user or the trusted soft
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However, the previous paragraph beg
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Table 1. Internet Engineering Task
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• Lightweight directory access pr
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mechanism to overcome the key distr
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Deployments that need to support mu
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Today’s Reality: Islands of Commu
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Simultaneously, IP addresses are al
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in-depth manner. Defense-in-depth m
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Protection Detection Reaction / Neu
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encrypted and then encapsulated wit
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Internet (grouping of autonomous sy
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via that same IP address. Specifica
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deployments. Regional flights that
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neighbor as a next hop after “Hol
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Interface Interface Customer Site S
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Interface Customer’s Application
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Although the vast majority of PBN s
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6. RELATING SAFETY AND SECURITY FOR
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6.1.1 Integrity. As section 4.3 ind
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As mentioned in section 4.4, the hi
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Page 97 and 98: their own classification level nor
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Page 107 and 108: in a Biba Integrity Model environme
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Page 111 and 112: (see section 9.10). A secure mechan
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Page 115 and 116: concept, which is needed to create
Page 117 and 118: 4. Learn from past mistakes. Poor d
Page 119 and 120: exemplar airborne network architect
Page 121 and 122: • Requirement 8: Biba Integrity M
Page 123 and 124: Figure 31 shows how the recommended
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Page 133 and 134: 8.3.5 Firewall. The firewall needs
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Page 139 and 140: 9.2 INTEGRATED MODULAR AVIONICS IMP
Page 141 and 142: 9.3 USING PUBLIC IPs. The model and
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Page 145: environments. If the certification
Page 149 and 150: elationship with other equipment in
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Page 163 and 164: 11.2 TOPICS NEEDING FURTHER STUDY.
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Page 171 and 172: the following is a pointer to a rel
Page 173 and 174: Department of Defense Instruction N
Page 175 and 176: Information Assurance—The Departm
Page 177 and 178: Threat source—Either (1) intent a
Page 179 and 180: information found within these data
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Page 187 and 188: authorized to perform. 13 However,
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Page 191 and 192: A.3.1 DENIAL OF SERVICE ATTACKS. Th
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A-15. Barbir, A., Murphy, S., and Y
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Survey Question What is the primary
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Survey Question What is the primary
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should be emphasized that there is
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