We present a novel scheme called Decentralized Attestation for Device Swarms (DADS), which is, to the best of 
our knowledge, the first to accomplish decentralized attestation in device swarms. Device swarms are smart, 
mobile, and interconnected devices that operate in large numbers and are likely to be part of emerging 
applications in Cyber-Physical Systems (CPS) and Industrial Internet of Things (IIoTs). Swarm devices process 
and exchange safety, privacy, and mission-critical information. Thus, it is important to have a good code 
verification technique that scales to device swarms and establishes trust among collaborating devices. 
DADS has several advantages over current state-of-the-art swarm attestation techniques: It is decentralized, 
has no single point of failure, and can handle changing topologies after nodes are compromised. DADS assures 
system resilience to node compromise/failure while guaranteeing only devices that execute genuine code remain 
part of the group. We conduct performance measurements of communication, computation, memory, and energy using 
the TrustLite embedded systems architecture in OMNeT++ simulation environment. We show that the proposed approach 
can significantly reduce communication cost and is very efficient in terms of computation, memory, and energy 
requirements. We also analyze security and show that DADS is very
effective and robust against various attacks.