Data Availability and Modular Blockchains

A valid block header proves nothing about whether the data behind it was actually published. That gap—the data availability problem—breaks fraud proofs, light clients, and rollup security in ways that aren’t obvious until something goes wrong. This chapter covers DAS, the erasure coding math underneath it, Celestia’s purpose-built DA architecture, the modular blockchain paradigm, EigenLayer restaking and its correlation risks, and when monolithic still beats modular. Here’s what it covers: