Methods, systems, and apparatus, including computer programs encoded on computer storage media, for enhancing blockchain network security. Embodiments include generating a request for data from a data source, the request including plaintext data and encrypted data, the encrypted data including access data and a hash of the plaintext data, transmitting the request to a relay system component external to the blockchain network, receiving a result from the relay system component that is digitally signed using a private key of the relay system component, and verifying an integrity of the result based on a public key of the relay system component and a digital signature of the result.