What can be found inside BlackCoin’s blockchain

Bitcoin-related cryptocurrencies contain the OP_RETURN opcode which can be used to create unspendable outputs, optionally containing some associated data. Usage of this opcode is generally not encouraged due to a threat of blockchain bloat, though if proper fee policy was introduced, it should do no harm. BlackCoin since version 1.2.3 contains a command named “burn” which creates such outputs.

I’ve written a simple Haskell application that inspects blockchain to find transaction outputs which use OP_RETURN. Using it, I’ve crawled BlackCoin’s blockchain from block 1 to 1697894. Some highlights:

• There are 559 transaction outputs using OP_RETURN.
• There are 559 transactions containing outputs which use OP_RETURN.
• 91 transaction outputs have actually burnt some coins.
• 76 transaction outputs have burnt the minimum possible amount of coins, 0.00000001 BLK.
• The largest amount of coins burnt is 2.4926 BLK.
• Transaction d6409e30fcf96d60aae807f5d68468fba03b4accf1fb13c257969a24d2d3f5a9 contains text “Happy 3rd birthday!”.
• Transaction 9ba558c64985d8452f4f65f47ea873d360e22e5697dcf6185125c4cbfaf4855b contains text “Big shout-out to janko33 for bringing Blackcoin to the 0.12 codebase |blackstat”.

Full results are available (paid in BLK), in the following format:

• transaction id;
• transaction output index;
• transaction output value (amount of coins burnt);
• script as hexadecimal string;
• decoded script.