A computer-implemented method comprising, by a given proxy node (230A-C): Receiving, via a computer network, a transaction generated and partially signed by an originator node, the transaction including a first input and a first and second output, wherein the first input takes x + r units of computing resources and wherein the first output provides x units to an output address and the second output provides d + r units to a 1-of-n multi-signature address unlockable using any one of a plurality of second private keys, each of the second private keys being associated with a respective one of a plurality of proxy nodes (230A-C), the plurality of proxy nodes (230A-C) including the given proxy node (230A-C), and each of the second private keys derivable by the respective one of the plurality of proxy nodes (230A-C) based on a private key of an asymmetric encryption key pair of that proxy node (230A-C) and a secret value that proxy node (230A-C) shares with the originator node; Selecting a quantity of computing resources, t units, to be allocated to the given proxy node (230A-C) for broadcasting the transaction and having the transaction included in a blockchain and selecting a quantity of computing resources, f units, to be allocated to a third-party for including the transaction in the blockchain, wherein f < r and t < ( r - f); digitally signing an updated transaction generated by adding a second input taking d + f units to the transaction; generating and digitally signing a further transaction including an input taking d + r units sourced from the 1-of- n multi-signature address using the second private key of the proxy node and an output providing t units to the given proxy node; and broadcasting the updated transaction and the further transaction, timed to permit their inclusion in the same block of the blockchain. Receiving, via a computer network, a transaction generated and partially signed by an originator node, the transaction including a first input and a first and second output, wherein the first input takes x + r units of computing resources and wherein the first output provides x units to an output address and the second output provides d + r units to a 1-of-n multi-signature address unlockable using any one of a plurality of second private keys, each of the second private keys being associated with a respective one of a plurality of proxy nodes (230A-C), the plurality of proxy nodes (230A-C) including the given proxy node (230A-C), and each of the second private keys derivable by the respective one of the plurality of proxy nodes (230A-C) based on a private key of an asymmetric encryption key pair of that proxy node (230A-C) and a secret value that proxy node (230A-C) shares with the originator node; Selecting a quantity of computing resources, t units, to be allocated to the given proxy node (230A-C) for broadcasting the transaction and having the transaction included in a blockchain and selecting a quantity of computing resources, f units, to be allocated to a third-party for including the transaction in the blockchain, wherein f < r and t < ( r - f); digitally signing an updated transaction generated by adding a second input taking d + f units to the transaction; generating and digitally signing a further transaction including an input taking d + r units sourced from the 1-of- n multi-signature address using the second private key of the proxy node and an output providing t units to the given proxy node; and broadcasting the updated transaction and the further transaction, timed to permit their inclusion in the same block of the blockchain.