A computer-implemented method comprising: encrypting a secret value under a public key associated with a mediator computer system; providing the encrypted secret value to a worker computer system (304, 404), wherein the encrypted secret value is usable by the worker computer system and the mediator computer system to collectively execute a first program; causing a second program to be made available on a blockchain data structure, wherein execution of the second program has an input; determining that the blockchain data structure reflects: a proof of correct execution of the second program; and an input value, wherein execution of the second program to generate the proof is based at least in part on using the input value as the input to the second program; determining, based at least in part on the proof, that the input is valid; and in response to determining that the input value is valid, providing the secret value to the worker computer system (304, 404), wherein the first program is executable using at least the secret value, wherein the method further comprises: generating a cryptographic hash output based at least in part on the secret value; generating an attestation that the encrypted value and the cryptographic hash output are both determined based at least in part on the secret value; providing the cryptographic hash output and the attestation to the worker computer system (304, 404), wherein the attestation is usable to determine whether the encrypted secret value and the cryptographic hash output are based at least in part on a same value. encrypting a secret value under a public key associated with a mediator computer system; providing the encrypted secret value to a worker computer system (304, 404), wherein the encrypted secret value is usable by the worker computer system and the mediator computer system to collectively execute a first program; causing a second program to be made available on a blockchain data structure, wherein execution of the second program has an input; determining that the blockchain data structure reflects: a proof of correct execution of the second program; and an input value, wherein execution of the second program to generate the proof is based at least in part on using the input value as the input to the second program; a proof of correct execution of the second program; and an input value, wherein execution of the second program to generate the proof is based at least in part on using the input value as the input to the second program; determining, based at least in part on the proof, that the input is valid; and in response to determining that the input value is valid, providing the secret value to the worker computer system (304, 404), wherein the first program is executable using at least the secret value, wherein the method further comprises: generating a cryptographic hash output based at least in part on the secret value; generating an attestation that the encrypted value and the cryptographic hash output are both determined based at least in part on the secret value; providing the cryptographic hash output and the attestation to the worker computer system (304, 404), wherein the attestation is usable to determine whether the encrypted secret value and the cryptographic hash output are based at least in part on a same value.