MultiChain Developer Q&A - Recent questions tagged op_return

OP_RETURN

Thu, 31 Jan 2019 08:03:14 +0000

Hii guys,

1)I just wanted to understand block hash which is created to generate block for example:
{
"hash" : "007466f9e7ff5d34ccc78b80ef55168706072f93b02d59ff6e60062ee12f22ae",
"miner" : "1HHqia9So9hJgXPqnQ5W5AP1CKN3Sn17iUu3sv",
"confirmations" : 82,
"height" : 10,
"time" : 1548850008,
"txcount" : 1
}
This is one block i have obtained from getblocks command so in that one hash is mentioned .
So my question is does that hash represent signature of blockchain?

2)I have gone through block signature in multichain you mentioned below setence
https://www.multichain.com/developers/mining-block-signatures/
Block signatures are embedded inside the OP_RETURN metadata of the coinbase transaction, using a regular bitcoin-style signature format. The payload signed by the block creator is the full block headers

can you explain me OP_RETURN opcode in simple example term i was trying to understand this opcode but i did not understand that is the reason i am asking this question here.
how OP_RETURN executed in block?

please help me to understand

uploading and retrieval of file from MC2.0 Alpha 3

Thu, 28 Jun 2018 19:02:47 +0000

Hi we are using multichain 2.0 alpha 3 version, as explained three parameters have been changed, we are able to crunch file upto 2 MB now, but while verifying/ retriving the file from streams, the values turn to be NULL, Pl help where are we wrong

in am not been able to find maxshowndata & gettxoutdata

{
"chain-protocol" : "multichain",
"chain-description" : "MultiChain chain1",
"root-stream-name" : "root",
"root-stream-open" : true,
"chain-is-testnet" : false,
"target-block-time" : 15,
"maximum-block-size" : 20097500,
"maximum-chunk-size" : 1048576,
"maximum-chunk-count" : 1024,
"default-network-port" : 9731,
"default-rpc-port" : 9730,
"anyone-can-connect" : false,
"anyone-can-send" : false,
"anyone-can-receive" : false,
"anyone-can-receive-empty" : true,
"anyone-can-create" : false,
"anyone-can-issue" : false,
"anyone-can-mine" : false,
"anyone-can-activate" : false,
"anyone-can-admin" : false,
"support-miner-precheck" : true,
"allow-arbitrary-outputs" : false,
"allow-p2sh-outputs" : true,
"allow-multisig-outputs" : true,
"setup-first-blocks" : 60,
"mining-diversity" : 0.300000000001,
"admin-consensus-upgrade" : 0.500000000001,
"admin-consensus-admin" : 0.500000000001,
"admin-consensus-activate" : 0.500000000001,
"admin-consensus-mine" : 0.500000000001,
"admin-consensus-create" : 1e-12,
"admin-consensus-issue" : 1e-12,
"lock-admin-mine-rounds" : 10,
"mining-requires-peers" : true,
"mine-empty-rounds" : 10.000000000001,
"mining-turnover" : 0.500000000001,
"first-block-reward" : -1,
"initial-block-reward" : 0,
"reward-halving-interval" : 52560000,
"reward-spendable-delay" : 1,
"minimum-per-output" : 0,
"maximum-per-output" : 100000000000000,
"minimum-offchain-fee" : 0,
"minimum-relay-fee" : 0,
"native-currency-multiple" : 100000000,
"skip-pow-check" : false,
"pow-minimum-bits" : 8,
"target-adjust-freq" : -1,
"allow-min-difficulty-blocks" : false,
"only-accept-std-txs" : true,
"max-std-tx-size" : 20097500,
"max-std-op-returns-count" : 32,
"max-std-op-return-size" : 20097152,
"max-std-op-drops-count" : 5,
"max-std-element-size" : 40000,
"chain-name" : "chain1",
"protocol-version" : 20003,
"network-message-start" : "f8e4f7ed",
"address-pubkeyhash-version" : "00a3a284",
"address-scripthash-version" : "0580bcad",
"private-key-version" : "801d6d29",
"address-checksum-value" : "c8835e5c",
"genesis-pubkey" : "034475839d78341a573659ab10ea846b568dacd5a3de19f379fb8c8855ded0170f",
"genesis-version" : 1,
"genesis-timestamp" : 1530198132,
"genesis-nbits" : 536936447,

First transaction in a block

Mon, 04 Sep 2017 13:18:23 +0000

What is this first transaction the block that is returned via OP_RETURN? Is this a transaction created by the mining node or is it just a creation transaction to create the block?

Multichain generate transaction(coinbase transaction)

Tue, 18 Apr 2017 06:22:42 +0000

What's in the scriptPubKey of generate transaction? I looked through the raw data of generate transaction and found an output with arbitrary data with OP_RETURN

0000000000000000 //bitcoin value
71   //scriptPubKey size 113
6a   //OP_RETURN
4c6e   //push 110 bytes
53504b624630440220771079e8b6a3fe0ef68b2303306d01d8326cb960c1859a056762056618dca2b502205b6020bb08f7c0b03e552fb530c4a0dbfd61ca7a6ef4e1113445c9415f377bf9022103217cf0819355518dd771228de6c9887cc1053e8fb9d2948262a7593e92390dfe
00000000 //locktime

What does this data contain, and what is this data for?

Standard Transaction Defenitions in params file

Mon, 06 Feb 2017 18:12:08 +0000

What should be the max-std-tx-size if OP_RETURN count = 10 and OP_RETURN size = 8MB?
(I have set max block size to 32 MB, should I decrease OP_RETURN count if max block size is 32MB? )

following are the entries in the params file:

# Standard transaction definitions

only-accept-std-txs = true              # Only accept and relay transactions which qualify as 'standard'.
max-std-tx-size = 4194304               # Maximum size of standard transactions, in bytes. (1024 - 10000000)
max-std-op-returns-count = 10           # Maximum number of OP_RETURN metadata outputs in standard transactions. (0 - 1024)
max-std-op-return-size = 8388608        # Maximum size of OP_RETURN metadata in standard transactions, in bytes. (0 - 8388608)
max-std-op-drops-count = 5              # Maximum number of OP_DROPs per output in standard transactions. (0 - 100)
max-std-element-size = 600              # Maximum size of data elements in standard transactions, in bytes. (128 - 32768)

OP_RETURN for data, prunable?

Thu, 02 Feb 2017 13:40:08 +0000

Hi, when using OP_RETURN to store arbitrary data, can the node be configured to prune that data?

Ideally the data should not be part of the data used to generate the hash of the transaction similar to Bitcoin.

How can i store file's hash in multicain

Mon, 27 Jun 2016 09:41:30 +0000

I want to create a blockchain where each user can store the hash of files, and everyone can check if a certain hash exists in the blockchain.
In order to acheive that i did some research and found that OP_RETURN allows users to assign metadata to transcations.

Is it correct to use this method or is there any alternatives (I'm new to the blockchain world)?

can someone tell me the command line to use?