The data availability problem

A problem that is concerned with whether the data in the proposed block can be verified that it is available. The problem commonly arises in sharded blockchains and with off-chain scaling solutions, L2s, because their architectures increase the attack vector for data withholding attacks.

While data availability is trivial for monolithic blockchains that do not scale, a more scalable modular approach introduces situations where ensuring data availability can become problematic.