The integration of Blockchains (BC) and Internet-of-Things (IoT) brings several benefits, such as data immutability and traceability, to a myriad of use-cases. The use of intermediary nodes, e.g., an edge node, provides benefits, but opens the possibility for attacks, especially when considering nodes handling the signing of transactions for devices. If the private key of a device is leaked, the data coming from that device cannot be trusted anymore, thus, rendering transactions signed with that private key unreliable.To tackle this concern, this paper presents Edge2BC, a practical approach to sign automatically BC transactions in an IoT device without revealing its private key to intermediary nodes, thus, increasing trust in the edge-to-BC data transit. The device relies on an edge node to communicate with a BC interoperability API to retrieve dynamic information (e.g., transaction nonce and gas price) and to send the signed raw transaction to the correct BC node. Power measurements (i.e., required current for different method steps) were performed in the prototype implemented to verify Edge2BC's feasibility. Such evaluations indicate that it is possible to have such a method in place, but the high power consumption required during the signing phase should be taken into consideration when deploying Edge2BC in a dedicated scenario.