Proxy digital signatures are a subset of proxy cryptography that enable a peer, as a proxy delegator, to delegate signing privileges to another trusted peer, who becomes a proxy signer. The proxy signer then signs authorized transactions routed to it from the proxy delegator, to then send to the intended third party on their behalf. This has great applications for computer networks where certain devices lack sufficient computational power to secure themselves and may rely on trusted and computationally more powerful peers, particularly within edge and fog networks. Although there are multiple proxy digital signature schemas that are circulated within cryptography-centric research papers, a practical software implementation has yet to be created. In this paper we describe Mengde Signatures: the first practical software implementation of proxy digital signatures. We expound upon the current architecture and process for how proxy signatures are implemented and function in a software engineering context. Although applicable to many different types of networks, we showcase the application of Mengde Signatures on an open source Proof-Of-Work Blockchain.