# Security Establishment in ADS-B by Format-Preserving Encryption and Blockchain Schemes
## 2 Literature Review  
ADS-B security issues have been a hot research topic for at least the past 10 years. Several encryption techniques have been proposed for the protection of ADS-B data [4]. These encryption schemes are classified as symmetric or asymmetric encryption based on the similarity and dissimilarity of the encryption and the decryption keys. A digital signature is a mathematical scheme for verifying the authenticity and the inverse function of public-key cryptography. The data is encrypted with a private key by the sender, and can then be decrypted with a public key by the receiver. A lightweight identity-based batch verification (IBV) signature scheme is suggested by [PERSON] et al. [13] to establish \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Attack** & **Attack Methods** & \begin{tabular}{c} **Attack Severity** \\ **Level** \\ \end{tabular} & \begin{tabular}{c} **Impacted** \\ **Requirement** \\ \end{tabular} \\ \hline \multirow{2}{*}{Passive attacks} & \begin{tabular}{c} Eavesdropping \\ Jamming \\ \end{tabular} & \begin{tabular}{c} Low \\ Medium \\ \end{tabular} & \begin{tabular}{c} Confidentiality \\ Availability \\ \end{tabular} \\ \hline \multirow{2}{*}{Active attacks} & \begin{tabular}{c} Message Injection \\ Message Deletion \\ Message Modification \\ \end{tabular} & \
\begin{tabular}{c} High \\ High \\ High \\ \end{tabular} &
\begin{tabular}{c} Authentication \\ Integrity \\ Integrity \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ADS-B attack classification. security via batch message identification. This IBV system has considerable resistance to replay attacks. According to their results, the method has a low computational load and a low transmission overhead. However, [PERSON] et al. 's proposal was not put into practice. In a broader work, [PERSON] et al. [14] examined the merits and drawbacks of both symmetric and asymmetric encryptions, digital signatures, and related key management. Their study concluded that symmetric encryption key management is difficult to control, and that the only feasible encryption technique is asymmetric encryption. Specifically, they determined that the Elliptic Curve Digital Signature Algorithm (ECDSA) signature length is the smallest length that should be applied. The ECDSA signature length is 448 bits, which makes the overall message length 560 bits. In the proposed approach, the message is divided into nine segments; the first segment has 112 bits, followed by eight 56-bit segments. Next, the signature is offered to be broadcast, either by other flight radio channels to support ADS-B, or via the distance measuring equipment (DME) channel that can be utilized to transmit ADS-B signed data. Both approaches reduced the delay of the transmitted message, but the message's length was still too long. These approaches are not recommended. Contrary to symmetric encryption, peer-to-peer communication is not needed for the key exchange in the public-key encryption approach. A message authentication procedure built on elliptic curve cryptography (ECC) and the X.509 certificate was proposed by [PERSON] et al. [15] and [PERSON] et al. [16]. Their proposal exploits the ECSDA technique to produce signatures for ADS-B messages. This approach offers ADS-B data integrity and non-repudiation. Although this solution is not costly, it is less scalable than the existing ADS-B system. [PERSON] [17] introduced a phased hybrid encryption method to fix the symmetric encryption key exchange limitation and to enhance encryption performance. This method applies encryption in two stages: key encryption and data encryption. Key encryption utilizes identity-based encryption, and therefore certificate management is not required. Data encryption employs symmetric encryption to optimize its advantages. Data encryption can thus be performed quicker and more effectively than public-key encryption.