Post by izuno on Mar 3, 2023 17:16:32 GMT 10
When P downloads the blockchain from N , P receives the modified transactions with the NIZK proofs and the statements for each block containing modified transactions. P then executes the following steps. For each block B , and for each redacted transaction in B , P runs the verifier of the NIZK. If the NIZK proof is not valid then P marks B as invalid. If the NIZK proof is valid or if there is no redacted transaction then P computes a Merkle tree as follows. For each non redacted transaction P puts in the leaf of the Merkle tree the hash of the transaction; for each redacted transaction, P extracts the hash h from the statement of the NIZK proof and uses this hash as leaf of the Merkle tree. P computes the root of the Merkle tree and considers B a valid block only if the computed Merkle root is equal to the Merkle root contained in the header of B downloaded from N .
If all checks are successful, then P assumes that the downloaded blockchain is correct. Notice that the consistency of the chain is guaranteed also by the NIZK proofs. Such proofs ensure consistency when a redaction is done for a transaction belonging to a block B , still leaving the Merkle root in the header of B unchanged. The only inconsistency that holds is between the old hash and the hash of the new redacted transaction but this inconsistency is fixed by the NIZK proof.
If all checks are successful, then P assumes that the downloaded blockchain is correct. Notice that the consistency of the chain is guaranteed also by the NIZK proofs. Such proofs ensure consistency when a redaction is done for a transaction belonging to a block B , still leaving the Merkle root in the header of B unchanged. The only inconsistency that holds is between the old hash and the hash of the new redacted transaction but this inconsistency is fixed by the NIZK proof.