## 3 A Security-Enhanced Authenticated Key-Agreement Protocol: SE-UAVAKA
### SE-UAVAKA Initialization Phase  
In the initialization phase of the protocol (SE-UAVAKA), the key-generation center generates global parameters (including elliptic-curve base points, global public keys, se  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Notation** & **Description** \\ \hline \(A\) & Agreement Entity \(A\) \\ \(B\) & Agreement Entity \(B\) \\ \(RC\) & Key-generation center \(RC\) \\ \(PK\) & Public key of the key-generation center \\ \(sk\) & Private key of the key-generation center \\ \(ID_{A},ID_{B}\) & Identification of the protocol entity \\ \(Z_{q}^{*}\) & Integers in finite fields \\ \(E(.)\) & Symmetric encryption function \\ \(D(.)\) & Symmetric decryption function \\ \(\oplus\) & Bitwise XOR Operator \\ \(TS\) & Timestamp information \\ \(H(.)\) & One-way hash function \\ \(SSK_{AB},SSK_{BA}\) & Session keys of protocol entities \\ \hline \hline \end{tabular}
\end{table}
Table 1: Some notations used in the protocols.  
lected one-way hash functions, and encryption functions) and then sends broadcast signals of the global parameters to each UAV device and ground station in the vicinity through a wireless channel.  
The individual steps of the initialization phase of the protocol are as follows:  
**Key-generation center RC**:  
1. Select a large prime number \(p\) and the parameters \(a,b\) as an elliptic curve \(E(a,b)\): A finite field exists on \(y^{2}=x^{3}+ax+b\) and satisfies \(4a^{3}+27b^{2}\
ot\equiv 0\pmod{p}\). The prime \(p\) is chosen to be sufficiently large (e.g., 256+ bits for modern security), while \(a\) and \(b\) are randomly selected from \(\mathbb{F}_{p}\) such that \(4a^{3}+27b^{2}\
ot\equiv 0\pmod{p}\), ensuring the curve is nonsingular (free from cusps or self-intersections) to maintain cryptographic integrity by avoiding singular points where discrete logarithm problems become computationally tractable.
2. Select point \(P\) as the base point of the elliptic curve. This point is selected because it generates a large cyclic subgroup of prime order, ensuring resistance to attacks like Pohlig-Hellman, and its cofactor is minimized to maintain cryptographic robustness.
3. Select a one-way hash function \(H(\cdot)\) (e.g., SHA-256, representing robust collision resistance and standardized security) and a symmetric encryption/decryption function \(E(\cdot),D(\cdot)\) (e.g., AES-128, ensuring strong confidentiality and widespread cryptographic acceptance).
4. Enter the ID (a constant identity ID that uniquely identifies the protocol instance, ensuring immutability and persistence throughout the device lifecycle) of the trusted protocol instance in the database (which is normally saved when the device leaves the factory;
5. Use a cryptographically secure pseudorandom number generator (CSPRNG, e.g., AES-CTR_DRBG from Linux/dev/urandom, FIPS 140-2 certified) to generate the global private key \(sk\in[1,n-1]\) (where \(n\) is the order of the elliptic-curve group), then compute the RC's global public key via scalar multiplication: \(PK=sk\cdot P\) (with \"\(\cdot\)\" denoting elliptic-curve scalar multiplication).
6. Transfer all public parameters \((E(a,b),p,P,PK,H(\cdot),E(\cdot),D(\cdot))\) to all protocol entities.