  "Code is law" is the funding principle of cryptocurrencies. The security,
transferability, availability and other properties of a crypto-asset are
determined by the code through which it is created. If code is open source, as
it happens for most cryptocurrencies, this principle would prevent
manipulations and grant transparency to users and traders. However, this
approach considers cryptocurrencies as isolated entities thus neglecting
possible connections between them. Here, we show that 4% of developers
contribute to the code of more than one cryptocurrency and that the market
reflects these cross-asset dependencies. In particular, we reveal that the
first coding event linking two cryptocurrencies through a common developer
leads to the synchronisation of their returns in the following months. Our
results identify a clear link between the collaborative development of
cryptocurrencies and their market behaviour. More broadly, our work reveals a
so-far overlooked systemic dimension for the transparency of code-based
ecosystems and we anticipate it will be of interest to researchers, investors
and regulators.
