1. A computer-implemented method for a secure execution of workflow tasks of a workflow to be executed according to a given execution pattern in a decentralized workflow system with a central workflow engine (CWE) initiating the workflow and a plurality of task execution agents (A 1 , A 2 ,.. .), wherein task-based public-private key pairs are produced using a workflow signature scheme, the method comprising, starting at an i'th execution agent which is selected by at least one preceding execution agent in accord with the execution pattern to perform an i'th task of the workflow, at least the following operations: receiving, from the at least one preceding execution agent via a secure channel, a task-based private key generated by the at least one preceding execution agent; signing workflow information of the workflow for at least one subsequent execution agent with a workflow signature, the workflow signature being computed using the workflow signature scheme by taking as input at least the task-based private key generated by the at least one preceding execution agent; selecting at least one appropriate subsequent execution agent; computing a task-based private key for the at least one subsequent execution agent wherein the task-based private key for the at least one subsequent execution agent is computed using system parameters and a workflow identifier assigned to the subsequent execution agent; and forwarding to the at least one subsequent execution agent the workflow information with its associated workflow signature, the system parameters and the task-based private key for the at least one subsequent execution agent through a secure channel.