Numerous applications in cryptography require the generation of random bits between two parties who do not trust each other on the way to proceed. Such a protocol is called a "coin flipping protocol". Research undertaken during the last decades showed that the realization of this task could not be achieved with an asynchronous quantum protocol. Indeed, the result can always be biased, at least partially. The protocol experimentally demonstrated here is based on special relativity and in particular on the impossibility of superluminal communication and its security against classical or quantum attacks is proved. However, as it is based on the synchronous exchange of random bits in two spatially separated location, agents of the two parties are required at each endpoint. It is therefore more interesting to reduce the distance which was done bellow the meter scale. This paves the way to miniaturization of such a system.