Abstract: Blockchain technology has revolutionized digital data management by providing a decentralized, unchanging and transparent structure for transaction recording. However, as blockchain systems are increasingly implemented in sensitive domains, such as finance, medical assistance, and supply chain management, the demand for advanced data security solutions becomes imperative. Traditional cryptographic algorithms such as RSA and EAS have been widely used to ensure digital communications, but each comes with limitations of scalability, computational efficiency and vulnerability to emerging threats. To face these challenges, this study proposes a new hybrid cryptographic structure that integrates RSA and AES algorithms to improve the safety and efficiency of blockchain-based data transactions. The proposed structure takes advantage of the capacity of RSA and AES for acute symmetric encryption to establish a safe and efficient encryption procedure in the blockchain environment. A wide architecture and algorithm model of the hybrid system is developed and implemented. Performance of this structure is evaluated using major standards such as encryption/decryption time, throughput, memory use and cryptonet resistance. Experimental results suggest that hybrid RSA-AES model, compared to standalone cryptographic methods, improves data privacy and transactions with minimal computational overhead compared to cryptographic methods. The integration of both algorithms significantly increases the speed of encryption, maintaining strong security protocols, making the system suitable for real-time blockchain applications. This research contributes to the growing field of secure blockchain structures, offering a scalable and practical solution that addresses the gaps in cryptographic efficiency and data protection. The results indicate that the proposed model can be an effective tool for strengthening blockchain transactions against sophisticated cyber threats. Future works will explore the integration of post-quantum cryptographic techniques and their adaptability to decentralized applications for long-term security sustainability.

Key words: blockchain security, cryptographic framework, RSA-AES hybrid encryption, secure data transactions, distributed systems