Distributed key secret for rewritable blockchain

A method comprising:

• accessing, in memory, a blockchain comprising:
• a selected block comprising original data;
• and
• a specific block comprising an integrity output, the integrity output determined from the original data as an input;
• at communication interference circuitry:
• performing a key secret exchange operation to receive portions of a key secret, the portions sent by multiple individually untrusted parties;
• receiving a command coordinated with the key secret exchange operation,
• the command specifying to overwrite the original data with altered data;
• and
• at rewrite circuitry:
• obtaining a portion combination from the portions of the key secret;
• determining whether a count of the portions exceeds a rewriting threshold for rewrite privileges;
• and
• when the count of the portions exceeds the rewriting threshold for rewrite privileges:
• computing collision data that includes the altered data, where:
• the collision data is coding-consistent with the integrity output, where overwriting the original data with the collision data does not introduce coding-inconsistency with the integrity output thereby preserving validity of the blockchain;
• and
• collision data is algorithmically determined from the portion combination and the altered data as inputs
• responsive to the command, overwriting the original data with the collision data.

A product comprising:

• machine-readable medium other than a transitory signal;
• instructions stored on the machine-readable medium, the instructions, when executed, configured to cause a processor to:
• access, in memory, a blockchain comprising:
• a selected block comprising original data;
• and
• a specific block comprising an integrity output, the integrity output determined from the original data as an input;
• at communication interference circuitry:
• perform a key secret exchange operation to receive portions of a key secret, the portions sent by multiple individually untrusted parties;
• receive a command coordinated with the key secret exchange operation, the command specifying to overwrite the original data with altered data;
• and
• at rewrite circuitry:
• obtain a portion combination from the portions of the key secret;
• determine whether a count of the portions exceeds a rewriting threshold for rewrite privileges;
• and
• when the count of the portions exceeds the rewriting threshold for rewrite privileges:
• compute collision data that includes the altered data, where:
• the collision data is coding-consistent with the integrity output, where overwriting the original data with the collision data does not introduce coding-inconsistency with the integrity output thereby preserving validity of the blockchain;
• and
• collision data is algorithmically determined from the portion combination and the altered data as inputs
• responsive to the command, overwrite the original data with the collision data.