Heavy proofs

This section explains the heavyproof object.

heavyproof

The heavyproof structure proves the finality of a block on a foreign blockchain, and it will contain four named top-level elements in its JSON object representation:

• chain_id: identifies the chain this proof originates from (string object with an Antelope chain ID value in hexadecimal).
• blocktoprove: object with the block that is being proven to be final.
• bftproof: array of objects that comprise the proof (that the block is finalized).
• hashes: an array of all hashes contained in the incremental merkle tree and merkle branches of the proof.

blocktoprove

This object contains:

• The block header,
• The block producer signature(s),
• The previous block merkle root, and
• The incremental merkle tree structure at the previous block height.

Example of a blocktoprove object:

{
        "block": {
          "header": {
            "timestamp": "2022-08-30T17:57:49.500",
            "producer": "eoseouldotio",
            "previous": "01ed944fd5774b924e89eaaa05c6b5f20257fb12f7d41cc3acb1fa283a52932b",
            "transaction_mroot": "5b0cb5a5ed6e7b25977bb0b823b4e0b2aefb3d8f8bd520caa3b9e0d04f8ef0b5",
            "action_mroot": "d227b326007b2704a2fb716ac3886fcffacfeaaaabfea6e2ef84bf6946dfed26",
            "confirmed": 0,
            "schedule_version": 45,
            "new_producers": null,
            "header_extensions": []
          },
          "producer_signatures": [
            "SIG_K1_KjPPNhS2KEAPg8gpk9XXaS27Zqd3fs9TesuAFswk4QpWUvp9ESYGMZbQvkbFCKfa6JtB98QmhJDXcicHRGQ5y9ZNR2XFBx"
          ],
          "previous_bmroot": "2b3e9633189d107d955701e87258a0de8f931620f7d820d548c1a44aae36e3d6",
          "id": "",
          "bmproofpath": []
        },
        "active_nodes": [
          0,
          1,
          2,
          3,
          4,
          5,
          6,
          7,
          8,
          9,
          10,
          11,
          12,
          13,
          14
        ],
        "node_count": 32347214
}

bftproof

This object contains the BFT proofs (Byzantine fault-tolerance proofs), that is, the proof that the blocktoprove is final according to the BFT consensus mechanism of the blockchain.

The object is an array of objects. Each object is composed of the following:

• header: a block header,
• producer_signatures: the block producer signature(s),
• previous_bmroot: the previous merkle root,
• bmproofpath: a list of merkle branches.

Under the current consensus model, a two-thirds supermajority of producers from the current scheduled set confirm each block twice. The first confirmation stage proposes a last irreversible block (LIB). The second stage confirms the proposed LIB as final. At this point, the block becomes irreversible.

The block producer for a given block implicitly confirms their block as valid, meaning 14 additional blocks signed by different block producers must be added to the block to complete a stage.

As an example, consider the standard Antelope configuration of 21 block producers. A valid BFT proof finality round must contain exactly 15 blocks signed by different block producers.

Since the block_to_prove counts for one in the first round, 14 BFT proofs must be added to seal the first round. Similarly, since the last BFT proof of the first round counts as the first one for the second round, 14 additional BFT proofs must be added to the array, for a total of 28 BFT proofs.

Example of a BFT proof component object:

{
          "header": {
            "timestamp": "2022-08-30T17:57:54.000",
            "producer": "eosnationftw",
            "confirmed": 240,
            "previous": "01ed9458124eb33ccca5994c5199389e6ebc4d7dcf3a80219e691fee19879bdc",
            "new_producers": null,
            "header_extensions": [],
            "schedule_version": 45,
            "transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
            "action_mroot": "166e0cbd9e48aeac5502c61c12a507b3b099823f5512ad26e73ffdc413a6b83d"
          },
          "producer_signatures": [
            "SIG_K1_Kh49gyGTZRUjYNJZbKbPwvuKDfr5ViWvoFstEQ85y6bNiXYqaEFLh5AMZMjn2tEFgh9EdmHX1THcMCuBCtpt3iN3A9WsX1"
          ],
          "previous_bmroot": "8d89791346fb91942edd7d63ba9337b7c9623332b0e5b0dda6630b1730a02912",
          "bmproofpath": [
            15,
            16,
            17,
            18,
            19,
            20,
            21,
            22,
            23,
            24,
            25,
            26,
            27,
            28,
            29,
            6,
            7,
            30,
            31,
            32,
            33,
            10,
            34,
            35,
            36
          ]
}

hashes

It is an array of all hashes contained in the incremental merkle tree (see active_nodes in blocktoprove) and merkle branches of the proof (see bmproofpath in bftproof).

Since many of these hashes are repeated throughout the proof, they are mapped using uint16_t indices instead, achieving a lossless compression ratio of between 20% and 80%, depending on the block height.

Example of a hashes array (abridged; these will usually be much longer):

[
        "f71f3caee388324520ecc34f3e1cc43068127aa1e2c7339db518094e69152490",
        "9c1b482433c921268cc0d35aa44cafa5727eece14b12ee419139e0e6c8c539c8",
        "f81e478eb2e76a7250689b0176d2e6099f20641a793c81278fdf2f9811ac32e6",
        "dec06b5072c38b764f50f0f36d71dfccfd034368c9804b72ce337edcc2e6c690",
        "84bf55aeebb5c05b8b2cbde58492bb3b201fff24501a84f0f71468a39343ae90",
        "d61cdcc9ec20c57acd35e9ccf00806d96ef347b6574fbe20d2a1039cfd52c07e",
        "7dd7116d4809bc6ff3bad85b7d83ac839b98e33f35c29c69a99cd9ecd5fa86cd",
        "6d2ac89b1d64d02dfa927db3c843896ebd4a03bd64cba239ce1386ef0d8a3c4e",
        "ef4daefc75f02402241cf0c4ff1e2005b2bf386c4de97ad138b73a767b087e78",
        "aa453c41aa2f3878c8ad949f76245255f5016b26f2ab3986e409e325eecee51f",
        "521023196e65a05183e7f91a5cefdc2ebb8fa3f265bb7f05792968fb1553fa63",
        "b259b8a5e302122fde20aed648f896ead3ee8cdaa397f7408b494ad5cda30263",
        "90ae8df1f23ab2c80276e7e1c30a32be45913f4c02a8ce3663745d16d12e7507",
        "b2320e40f0ac29475fede29002678a667f39664ff0891c406d64b4c7573dbd20",
        "9db19461c8416b3ad6c0352c09cc3a43d7c04ef6724f201c9268aa59d2e5f0f8"
]