Erasing Data from Blockchain Nodes

Abstract

It is a common narrative that blockchains are immutable and so it is technically impossible to erase data stored on them. For legal and ethical reasons, however, individuals and organizations might be compelled to erase locally stored data, be it encoded on a blockchain or not. The common assumption for blockchain networks like Bitcoin is that forcing nodes to erase data contained on the blockchain is equal to permanently restricting them from participating in the system in a full-node role. Challenging this belief, in this paper, we propose and demonstrate a pragmatic approach towards functionality-preserving local erasure (FPLE). FPLE enables full nodes to erase infringing or undesirable data while continuing to store and validate most of the blockchain. We describe a general FPLE approach for UTXO-based (i. e., Bitcoin-like) cryptocurrencies and present a lightweight proof-of-concept tool for safely erasing transaction data from the local storage of Bitcoin Core nodes. Erasing nodes continue to operate in tune with the network even when erased transaction outputs become relevant for validating subsequent blocks. Using only our basic proof-of-concept implementation, we are already able to safely comply with a significantly larger range of erasure requests than, to the best of our knowledge, any other full node operator so far.

Blockchain for power systems: Current trends and future applications

“…The block immutability contrasts with the right to be forgotten provided by GDPR. There are three possible approaches for tackling this inconsistency, (i) data are stored off-chain and their cryptographic hash on the blockchain; (ii) to store encrypted data on the blockchain, then destroy the key in case these data have to be forgotten; (iii) use cryptographic approaches for erasable blocks [48], [49] . The first two solutions have some drawbacks: in the first, data availability is not guaranteed, in the second case an attacker could have in the future enough computational power to break the encryption scheme.…”

Runtime Hook on Blockchain and Smart Contract Systems

“…There are several approaches [1,2,7,13,27,35] to limiting inappropriate blockchain transactions. One approach [1] is to filter and discard a transaction before the transaction being committed to the blockchain, and possibly redact transactions from blockchain.…”

“…One approach [1] is to filter and discard a transaction before the transaction being committed to the blockchain, and possibly redact transactions from blockchain. Another approach [2,7,13,27] is to redact a transaction after it has mined in the blockchain. And the other approach [34] uses a log-based framework to monitor blockchain systems' real-time performance.…”

Modifiable Public Blockchains Using Truncated Hashing and Sidechains

“…Attempts to have more decentralized approaches on modifiable blockchain can be found in [32]- [38]. In their works, the blockchain that can be modified is said to be 'rewritable', 'editable', 'redactable', 'modifiable' or 'mutable'.…”

“…Florian et al [38] proposed a functionality-preserving local erasure (FPLE) approach which is capable of erasing data from the local node. The study demonstrated the deletion of local data through a Bitcoin implementation by empowering node operators (private blockchain).…”