Verifying distributed erasure-coded data

Erasure coding can reduce the space and band width overheads of redundancy in fault-tolerant data storage and delivery systems. But it introduces the fundamental difficulty of ensuring that all erasure-coded fragments correspond to the same block of data. Without such assurance, a different block may be reconstructed from different subsets of fragments. This paper develops a technique for providing this assurance without the bandwidth and computational overheads associated with current approaches. The core idea is to distribute with each fragment what we call homomorphic fingerprints. These fingerprints preserve the structure of the erasure code and allow each fragment to be independently verified as corresponding to a specific block. We demonstrate homomorphic fingerprinting functions that are secure, efficient, and compact.