The Walking Dead Drops

What is WaDeD?

Dead drops

WaDeD stands for Walking Dead Drops. A dead drop is an old espionage method. It consists in leaving a message in a secret location known only by two people. At a specific moment, one of them will drop a message and the other will come later to get it. This principle having evolved with technology, it is not uncommon nowadays to see a USB key used as a dead drop, fixed in concrete in a wall.

WaDeD looks to pushing this principle further, by using what modern radio technology can offer. There are two sorts of devices that differ in the way they are used. The first kind are fixed devices, like dead drops, but wireless. They hold small messages that people want to leave for other people to pick up. The other kind are mobile devices, that people carry with them and can drop and pick up messages to and from the dead drops.

We can do better, though. Being forced to move to the exact location where the message was dropped can be a pain, and broadly under-exploits the potential of a lot of people carrying small radio devices on them all the time to drop and pick up messages. That is why in WaDeD, every device becomes a dead drop, relaying the messages from one user to another without its owner even noticing it. Some of the drops really are dead drops (that is, unmoving, hidden somewhere to serve as a relaying point); some are walking dead drops, since they are moving with their owners. Hence the name.

The principle

A WaDeD network aims to provide a simple and efficient way of exchanging short messages between its users. Its main component is a board of our conception, with a low consumption microprocessor, an external memory to store the messages, a transciever and a long antenna to communicate over the radio, and a micro USB port to plug it to another device.


On the network level, the devices carry messages with informations about the expeditor and the recipient. When two devices meet, they exchange all of the messages they are carrying with them. A device plugged to a host automatically sends him all the messages that are intended for him. Since all the nodes in the network play the role of a relay for messages, WaDeD is a mesh network. Its structure varies constantly, so there is no guarantee that a message will ever reach its recipient. However, since messages flood the network until they reach him, chances for a single message to actually be delivered are maximized.

Two devices synchronize their messages with a pretty smart algorithm that uses very few radio exchanges. The overall goal of lowering the consumption is to be able to leave the dead drops run on its own for long periods of time without the need of a network administrator to change the battery. Because of the nature of the communication protocol, a large number of devices can be communicating all together at the same place without performance losses, and be synchronized all together rather quickly.

Currently the only client we have runs on personal computers, because Android usually do not allow USB on the go technology to be used. In the future, clients that work on other platforms might be developed.