Sphere 10 has designed a deletable blockchain technology that allows blockchain-based systems to maintain a small and constant storage footprint.
Simply put, a deletable blockckain is a blockchain where new blocks are appended to the top and old blocks are deleted from the bottom whilst retaining the security of the full chain. Since only the last few blocks are stored, nodes effectively store the “flow of transactions” rather than the infinite history.
As a result, such systems can run for indefinite periods of time, at maximum speed, using a constant storage. Thus they achieve “Infinite Scalability”.
The technology works by segregating “state data” into a separate data-structure and requiring blocks to commit to that data-structure and the previous block. In this manner, nodes can independently verify the “aggregated proof-of-work” without ever requiring old blocks. Since the state-data is maintained in a separate data-structure, old blocks are never required for transaction verification.
This aggregated proof-of-work technique is currently being used by PascalCoin to secure it’s SafeBox. It can also be applied to traditional blockchains as a UTXO Commitment Scheme.