# HAE: A Hybrid Cryptographic Algorithm for Blockchain Medical Scenario Applications
## 4 Experiments and Analysis
### Experimental Analysis
#### 4.4.1 Security Analysis  
The hybrid cryptographic algorithm HAE employs AES for data encryption and ECC for AES key encryption, offering enhanced security compared to the traditional AES algorithm. In the conventional AES algorithm, the same key is used for encryption and decryption operations, making key security crucial. In contrast, HAE uses ECC to encrypt the AES key, leveraging the benefits of asymmetric encryption to provide a higher level of key protection. HAE employs ECC asymmetric encryption in the key exchange and data transmission processes, offering stronger resistance to attacks, particularly against specific attacks targeting the symmetric encryption algorithm AES, such as cryptanalysis and exhaustive search attacks. Even if attackers manage to crack the AES algorithm, they will still need to decrypt the AES key to access the data. Moreover, both the AES and ECC algorithms are inherently secure. AES employs a multi-round iterative network structure that combines complex mathematical operations with nonlinear transformations to achieve robust obfuscation and diffusion properties. AES supports various key lengths, including 128-bit, 192-bit, and 256-bit, with longer key lengths offering higher security. AES has undergone extensive cryptographic analysis and evaluation, and there is no publicly available effective attack method capable of breaking full-round AES encryption. The current best-known attack methods target AES variants with fewer rounds using approaches such as brute force exhaustion, as shown in Table 3. For full-round AES encryption, as long as the key is strong enough, it is theoretically considered secure. The security of ECC is based on the elliptic curve discrete logarithm problem, and there is no effective attack method within the current scope of mathematical knowledge and related algorithms. Therefore, using ECC encryption to protect the AES key is considered safe. In the context of blockchain-based medical applications discussed in this paper, the combined encryption techniques of AES and ECC ensure the protection of medical data during both transmission and storage. Specifically, the use of ECC encryption safeguards the  
Figure 8: Initial medical data.  
AES key. Consequently, crypto-attackers cannot access the AES key's details, rendering them incapable of decrypting the ciphertexts. This strategy effectively ensures the security of the medical data. The encrypted data are stored within the IPFS. Any unauthorized alterations to this encrypted data are promptly identified during decryption, as such modifications result in an output that diverges from the original data. Nodes within the blockchain retain the file address hash provided by IPFS. Leveraging public key encryption, timestamps, node consensus, and other advanced technologies, the blockchain guarantees the immutability of data on the chain. This comprehensive approach ensures the medical data's confidentiality, integrity, and authenticity. In summary, AES provides efficient data encryption and decryption, while ECC offers robust key protection. Combining the two into a new hybrid cryptographic algorithm ensures both data and key protection, delivering more comprehensive security.