<p>The advancement of quantum attacks has posed a significant threat to blockchain cryptosystems. Furthermore, the finite lifecycles of ciphertext and keys may result in data leakage risks for long-term storage due to potential breaches in ciphertext security, necessitating ciphertext updates. Ensuring the long-term security of cryptographic algorithms on blockchains against quantum attacks has emerged as a critical concern in blockchain research. A blockchain oracle serves as a mechanism for data communication. The Module-Learning with Errors (MLWE) problem is a significant issue in lattice-based cryptography, providing security against quantum attacks. To resist the threat of quantum attacks on encrypted data and ensure the long-term security, this study proposed an updatable encryption (UE) scheme for blockchain oracles based on post-quantum cryptography. First, this study developed a UE scheme based on the blockchain oracle architecture, enabling the oracle to update encrypted data via update tokens, ensuring the data's long-term security. Additionally, a UE algorithm based on the MLWE problem was introduced to enhance its resistance to quantum attacks. Finally, an error-correcting mechanism tailored for the UE algorithm was developed to validate transmitted data, correct errors, and improve the scheme's robustness. The experimental results demonstrate that the proposed scheme not only provides quantum-resistant security but also enables ciphertext updates through update tokens. Compared to existing schemes, it has more advantages in protecting data security.</p>