Difference between revisions of "OP RETURN"

Revision as of 08:23, 22 January 2020

OP_RETURN is a script opcode used to terminate the script and return the top value on the stack. This opcode is analogous to the return function in programming languages. The OP_RETURN opcode has a controversial history in Bitcoin and as a result has been primarily used as a means of storing data on the blockchain.

OP_RETURN Functionality

OP_RETURN terminates the script leaving the stack as-is and letting the result on top of the stack determine the success or failure of the script. OP_RETURN can be used in combination with flow control opcodes to implement branching, conditional logic in scripts.

Example

The below script is a metanet node that attaches the Metanet data to a UTXO with funds. This can be used to ensure that metanet nodes are left in the UTXO set

𝑇𝑥𝐼𝐷_{𝑛𝑜𝑑𝑒}
Inputs	Outputs
<sig_metaParent> <pubKey_metaParent> <sig_script> <pubKey_script>	DUP HASH160 <pkh_script> EQUALVERIFY CHECKSIG RETURN <meta> <pk_metaNode> <txid_metaParent>

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 '''OP_RETURN''' is a [[Opcodes_used_in_Bitcoin_Script|script]] opcode used to terminate the script and return the top value on the stack. This opcode is analogous to the return function in programming languages. The OP_RETURN opcode has a [[History_of_OP_RETURN|controversial history]] in Bitcoin and as a result has been primarily used as a means of storing data on the [[block_chain|blockchain]].
-In 2010 an exploit was discovered in Bitcoin where users could steal anyone's funds leveraging the OP_RETURN opcode. [[Satoshi_Nakamoto|Satoshi Nakamoto]] modified the opcode to always return false as an urgent fix.
-=== Return to original functionality ===
-The [[Genesis_upgrade|Genesis upgrade]] in February 2020 restores the original functionality of the opcode. This will not impact the ability to store arbitrary data on-chain, and it is advised to now use [[False Return]] scripts for applications that still seek to do so.
-The Genesis upgrade essentially re-enables the original functionality of the push data opcodes via lifting the maximum transaction size such that using a so-called 'OP_RETURN output' is no longer the only means of adding large data items such as JSON formatted text or images into a transaction.
-Reverting to the ability to return a value will enable more robust scripts to be created; for example scripts can now return different values based on conditional logic.
 ===OP_RETURN Functionality===

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Difference between revisions of "OP RETURN"

Revision as of 08:23, 22 January 2020

OP_RETURN Functionality

Example