Malleable coding with fixed segment reuse

In cloud computing, storage area networks, and remote backup storage, stored data is modified with updates from new versions. It is desirable for the data to not only be compressed but to also be easily modified during updates, since representing information and modifying the representation are both expensive. A malleable coding scheme considers both compression efficiency and ease of alteration, promoting codeword reuse. We examine the trade-off between compression efficiency and malleability cost-the difficulty of synchronizing compressed versions-measured as the length of a reused prefix portion. Through a coding theorem, the region of achievable rates and malleability is expressed as a single-letter optimization. Relationships to common information problems are also described.