Proof of Existence of a Block

Path in ledger query

This type of query is used to prove that block X is connected to block Y, based on skip chain hashes. The query result contains a list of block headers, including block X, connecting blocks, and block Y. X > Y, because connectivity in skip chains, like in all blockchains, is from latter block to the earlier one. For more information about ledger consistency, see the sections on Block Skip Chain and Block Structure.

Server expose ledger/path?start={startNum}&end={endNum} GET query to access to ledger paths.

Sign json serialized query

bin/signer -data '{"user_id":"alice","start_block_number":1,"end_block_number":6}' -privatekey=deployment/sample/crypto/alice/alice.key

Signature

MEYCIQC6C8c4NBgnfAEC0L5ftPOQqxbP53rypSHKL+oZ7O5cggIhAPyz1Jg8Dlv98XVDM6GaN9D17X0XiVvA7D2l8cibXcYr

Submit query

curl \
     -H "Content-Type: application/json" \
     -H "UserID: alice" \
     -H "Signature: MEYCIQC6C8c4NBgnfAEC0L5ftPOQqxbP53rypSHKL+oZ7O5cggIhAPyz1Jg8Dlv98XVDM6GaN9D17X0XiVvA7D2l8cibXcYr" \
     -X GET -G "http://127.0.0.1:6001/ledger/path" -d start=1 -d end=6 | jq .

Output

{
  "response": {
    "header": {
      "node_id": "bdb-node-1"
    },
    "block_headers": [
      {
        "base_header": {
          "number": 6,
          "previous_base_header_hash": "TJYT7zr95D3ghtU/M+j8OStU6r8Y+XRC5xfb90jshbI=",
          "last_committed_block_hash": "r57EtiB2XO1XlVAxBwFtn7cHP7YsfUBFi69y0UY0tw0=",
          "last_committed_block_num": 5
        },
        "skipchain_hashes": [
          "r57EtiB2XO1XlVAxBwFtn7cHP7YsfUBFi69y0UY0tw0="
        ],
        "tx_merkle_tree_root_hash": "dSc42JVp36bfORFO8QehzQFypEtBQfUzluT6ixhjeo4=",
        "state_merkle_tree_root_hash": "YRsFw5PcG1XzYO5o5nJa3lVfknijRqu6cCaDF1zpPA8=",
        "validation_info": [
          {}
        ]
      },
      {
        "base_header": {
          "number": 5,
          "previous_base_header_hash": "NqyVWNBl/XmWLM7PkK8NbI0qrwFmYvGHSTc03vj/zus=",
          "last_committed_block_hash": "nDNWHZPrlG3JVq6eLcuHPaS1iEZkBkemV7IleIVx6Jc=",
          "last_committed_block_num": 4
        },
        "skipchain_hashes": [
          "nDNWHZPrlG3JVq6eLcuHPaS1iEZkBkemV7IleIVx6Jc=",
          "wZmtCr8rJp/NGsEDjySSfHhi7Omr2Yw/d8rUaetrzLE=",
          "tl3PgPL/E52yhCWG1vLGk/bJXRqhw3rDxSXZzvMcuWo="
        ],
        "tx_merkle_tree_root_hash": "UXXqKu/I2Vr0Ma5cV9Hfun4Xo5285ZwdV9jcKspTnJo=",
        "state_merkle_tree_root_hash": "ksPp+NOrYLi909AYgrmrmGN1DKuez8ItpRJeLFpWy9g=",
        "validation_info": [
          {}
        ]
      },
      {
        "base_header": {
          "number": 1
        },
        "tx_merkle_tree_root_hash": "1XYyyOxBKRKw/vHgGGClrbko+wjkHmgzkWIjWEqoGaU=",
        "state_merkle_tree_root_hash": "Gxq3k91oLlxknN9VJCBEnc9IFnJU7YKGbiKtbQLMDF0=",
        "validation_info": [
          {}
        ]
      }
    ]
  },
  "signature": "MEQCIF1CZuJcUOBG3IkFIo0YkoB6+6X6HvUYaPX4KF/MoIScAiB8L13Da+5rKta9L+kggWJlp9uwsHSt2mQJ/tWliTeliQ=="
}

As you can see, block 6 points to block 5 and block 5 to block 1 (Genesis)

It's worth mentioning that block numbering in Orion starts from 1 and not from 0. All power two operations related to block number, require decreasing block number by 1.