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Questions tagged [opcodes]

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How is tapscript different than P2PKH using opcodes from a developer perspective?

I'm going to use ordinals as an example because they illustrate my question the most effectively. My understanding is that ordinals are created by writing opcodes into the transaction just like you ...
ChristianOConnor's user avatar
1 vote
1 answer
73 views

Is there any way for a script to depend on blockchain info?

The locktime opcodes OP_CHECKLOCKTIMEVERIFYand OP_CHECKSEQUENCEVERIFY indirectly allow for an approximate block number check, is there any way to obtain other information such as the previously mined ...
Tobias Kienzler's user avatar
2 votes
1 answer
140 views

If no push opcode, how does item still end up on stack (tx verification)

I was reading the following link and there it says: "Alice’s pubkey script then pushes the pubkey hash that Bob gave her for the first transaction". I mean how ? there's no opcode for that. ...
Giorgi Lagidze's user avatar
2 votes
1 answer
110 views

Can OP_DROP be used to include arbitrary data?

I have recently been looking into OP_RETURN and its uses in so far as including data in a transaction. Given the fact that OP_RETURN is limited to 80 bytes I thought what if OP_DROP was used? That way ...
user2334659's user avatar
2 votes
1 answer
273 views

What was the OP_IF opcode used for (except Lightning) before 2023?

There is the OP_IF opcode in Script. What did users use the OP_IF opcode for (use cases except for Lightning) before 2023? What tools to use to extract the transactions (with OP_IF) from historical ...
Greg Tonoski's user avatar
0 votes
1 answer
109 views

What is an "empty vector" in Bitcoin?

EDIT: Pieter Wuille gave an answer (look at the comments) to the last situation (with OP_CHECKSIG). OP_CHECKSIG is pushing 0x00. E.g. OP_0 pushes the empty vector, which represents the number 0 (to ...
Cosmos's user avatar
  • 199
1 vote
1 answer
124 views

Is the signature check performed when the signature is the empty vector?

In this answer Vojtěch Strnad wrote the following: OP_CHECKSIGADD always performs one check per signature, since unused public keys are required to be paired with an empty witness item and are ...
Cosmos's user avatar
  • 199
3 votes
2 answers
591 views

Undefined opcodes in bitcoin core defined as "Synonyms for OP_RETURN" in rust-bitcoin

In rust-bitcoin, opcodes past the 0xba opcode are named as such: OP_RETURN_187, OP_RETURN_188, ..., OP_RETURN_254. Their description is all the same: Synonym for OP_RETURN. The definition for ...
thunderbiscuit's user avatar
2 votes
1 answer
153 views

Is OP_CODESEPARATOR disabled in Bitcoin and if so why?

OP_CODESEPARATOR is used in the Bitcoin script language to mark the beginning of signature-checked data. However, the given operator never found its real practical use case. So, is the given operator ...
dassd's user avatar
  • 1,079
8 votes
1 answer
329 views

Why are OP_MUL and OP_DIV disabled in Bitcoin?

What is the reason why OP_MUL and OP_DIV operators were removed from Bitcoin? Is this because someone could maliciously create a script that multiplies large numbers and thus blows the stack, or is ...
dassd's user avatar
  • 1,079
1 vote
0 answers
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Scripting an escrow transaction where the arbitrator ALWAYS gets paid

I am trying to make an Escrow and Arbitration where the arbitrator always gets paid say 5% of the transaction. As in the famous escrow example here: Charlie-the-customer wants to buy a product from ...
Farahats9's user avatar
  • 111
2 votes
1 answer
67 views

Is it possible to create an output locked to a specific mining difficulty target?

When the network sees a block appear with enough difficulty nodes can detect this as potentially the longest valid chain allowing the blocks miner to officially claim the block reward via coinbase ...
Poseidon's user avatar
  • 643
2 votes
1 answer
125 views

Bitcoin Script Puzzle

I found this script puzzle post by ValentinoZ: https://twitter.com/vazertuche/status/1691814230129848473 I've tried solving it and can't seem to get it. I get stuck at the op_equalverify for the hash ...
Marco's user avatar
  • 395
3 votes
3 answers
656 views

What are MATT opcodes?

There is plenty of discussion in the Bitcoin-dev mailing list about MATT opcodes, and I would like to know what these are.
Eoin's user avatar
  • 335
2 votes
1 answer
185 views

How do I use python-bitcoin-utils to add an OP_RETURN message into a bitcoin transaction?

I have the following code that successfully created a bitcoin transaction with python-bitcoin-utils: from bitcoinutils.utils import to_satoshis from bitcoinutils.setup import setup from bitcoinutils....
ChristianOConnor's user avatar
1 vote
2 answers
315 views

What are the OP codes associated with bc1?

As the title says I'm trying to extract bc1 addresses by using opcodes I've found from reading about bitcoin online. However, I cannot actually find the opcodes associated with bc1. The segwit outputs ...
bitcoinluvr6969's user avatar
2 votes
1 answer
140 views

How come an `OP_3` P2SH redeem script is spendable?

I completed a round trip transaction with the redeem script hash: 31vFvEkyAb2iusbPip36H9rVt6pxExuaVR, whose redeem script is OP_3 (0x53) (yes I know not secure). I can understand OP_1 redeem script ...
Peter's user avatar
  • 115
2 votes
1 answer
234 views

Can any Script opcode be used in the witness program, or only specific ones?

I was wondering, can one use an OP_RETURN in the witness script? If not, why not? Also, how could I figure this out from reading Bitcoin Core source? I looked at this file, and it wasn't quite clear ...
Hunter Beast's user avatar
2 votes
2 answers
205 views

What are the risks of OP_VAULT?

In the past it has been argued that some covenant schemes could be risky. However AFAIK OP_VAULT is a very specific and limited construction. What are the risks associated with it, if any?
Son Kaos999's user avatar
2 votes
3 answers
299 views

A question about the role of OP_DUP in the P2PK(H) transaction specification, and possibility of slightly smaller single address transactions

Original Thread: Why OP_DUP instead of providing the PubKey twice in P2PKH? I am struggling to understand the logic in the most popular answer and my "reputation" is < 50 so I cannot ...
Poseidon's user avatar
  • 643
2 votes
1 answer
119 views

What is OP_RETURN_252?

The first scriptsig opcode in this coinbase transaction is OP_RETURN_252, followed a bit later by a OP_RETURN_188. These don't show in this list of opcodes. Digging the internet, I found this rust lib ...
RooSoft's user avatar
  • 157
0 votes
1 answer
113 views

Why is there a OP_NUMEQUAL opcode? Does OP_NUMEQUAL offer a subset of the functionality of OP_EQUAL?

There is a OP_EQUAL opcode that returns (from the Bitcoin wiki): 1 if the inputs are exactly equal, 0 otherwise And a OP_NUMEQUAL opcode that returns: 1 if the numbers are equal, 0 otherwise In ...
Michael Folkson's user avatar
0 votes
1 answer
273 views

How does the CHECKSIGADD opcode work? How does it compare to its predecessor CHECKMULTISIG?

How does the CHECKSIGADD opcode (defined in the Tapscript BIP) BIP342 work? How does it compare to its predecessor CHECKMULTISIG? The design of CHECKSIGADD was discussed in this StackExchange question....
Michael Folkson's user avatar
4 votes
2 answers
417 views

Why do invalid signatures in OP_CHECKSIGADD not push to the stack?

I've been working through the static test vectors provided by bitcoin core to implement an interpreter. Some surprising behavior I found was that in the case of OP_CHECKSIGADD, if an invalid signature ...
Chris Stewart's user avatar
2 votes
1 answer
239 views

Why does `OP_CHECKSIGADD` allow TAPROOT keyspends?

My understanding is this sig version is only for taproot keyspends, why is it allowed to be used in OP_CHECKSIGADD? https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/...
Chris Stewart's user avatar
7 votes
2 answers
574 views

Was the addition of OP_NOP codes in Bitcoin 0.3.6 a hard or soft fork?

I'm doing some deeper research into historical consensus changes and it seems like most folks consider the addition of the OP_NOP codes to be a hard fork. Here's the diff for their addition: https://...
Jameson Lopp's user avatar
4 votes
1 answer
264 views

Why isn't `OP_CHECKMULTISIG` compatible with batch verification of schnorr signatures?

BIP342 defines OP_CHECKSIGADD as a replacement for OP_CHECKMULTISIG. In the footnote it's mentioned that OP_CHECKMULTISIG is not compatible with batch verification, but I can't understand why and I ...
David A. Harding's user avatar
1 vote
2 answers
169 views

Why does this not return TRUE?

scriptSig: <pubKey> scriptPubKey: <pubKey> OP_EQUALVERIFY The stack has <pubKey>, <pubKey> and then OP_EQUALVERIFY. So why, does it not return TRUE, even when the recent two ...
Vedant Bhandare's user avatar
1 vote
1 answer
156 views

Is it possible to design a recursive covenant opcode that results in a full node stuck in an infinite verification loop?

Is it possible to design a new opcode enabling recursive covenants that could result in a full node stuck in an infinite loop of verifying transactions? (Obviously this would never be considered for a ...
Michael Folkson's user avatar
0 votes
1 answer
151 views

Why is OP_XOR disabled? Are there any forks on which it has been enabled? [duplicate]

Why is OP_XOR disabled? Are there any forks on which it has been enabled? Are there any plans to enable it? Perhaps this is the answer, still perhaps there is another reason for the bitwise logic ...
Lee's user avatar
  • 590
2 votes
1 answer
1k views

How to check OP_CHECKLOCKTIMEVERIFY?

I try to simply get into the OP_CHECKLOCKTIMEVERIFY opcode and test it. However I get the error error: Locktime requirement not satisfied no matter what unix- or blocktime I enter in my btcdeb. I ...
zerotobtc's user avatar
  • 323
2 votes
1 answer
184 views

Meaning of "Drop the signature" comments in OP_CHECKSIG code (Bitcoin v0.1.0)

I'm doing my homework by reading the C++ code of the 0.1.0 release of Bitcoin available here. I'm interested in better understanding how to validate transaction 1 of block 170. This transaction has ...
StashOfCode's user avatar
2 votes
2 answers
222 views

Elements (/Liquid) Tapscript opcodes

Related question: What opcodes are supported on Liquid but not yet on Bitcoin? I had seen few opcodes in the slides shared by notgrubles on Twitter. They are: OP_INSPECTCURRENTINPUT OP_INSPECTINPUT ...
user avatar
2 votes
1 answer
244 views

What opcodes are supported on Liquid but not yet on Bitcoin?

What opcodes are supported in Liquid as of today (September 2021) but not (yet) on Bitcoin? What is the rationale for including these particular opcodes but not others?
Michael Folkson's user avatar
2 votes
1 answer
370 views

What prevents OP_SUCCESS from being used nefariously?

If a script is automatically valid when an OP_SUCCESS opcode is called, what mechanism prevents a malicious actor from taking a random UTXO and creating a fake scriptsig with an OP_SUCCESS included?
Bertram Lund's user avatar
8 votes
2 answers
1k views

What are the downsides to enabling potentially suboptimal or unused opcodes in a future soft fork?

It appears to me that there are various ways to build covenants and vaults with opcodes and sighash flags that are not yet enabled in Bitcoin (e.g. OP_CHECKTEMPLATEVERIFY, SIGHASH_ANYPREVOUT, OP_CAT). ...
Michael Folkson's user avatar
7 votes
1 answer
814 views

Inner working of OP_IF and OP_ELSE

How does OP_ELSE work exactly? Is there an else if in Script? According to https://en.bitcoin.it/wiki/Script#Flow_control, the statements after an OP_ELSE are executed in three cases. It says: If ...
orfeas's user avatar
  • 103
1 vote
1 answer
70 views

Script: How to check if the top item on the main stack is numeric or not?

I'm looking for the clearest way to check whether the top element of the stack is numeric or not. Thank you in advance
FraMog's user avatar
  • 41
2 votes
1 answer
579 views

Is there a difference between OP_PUSHBYTES and OP_PUSHDATA

In some documentation about Script we sometimes have to use OP_PUSHBYTESx or OP_PUSHDATAx to indicate that some number of bytes will be an element to read. They seem to do the same thing so is there a ...
Saxtheowl's user avatar
  • 2,800
2 votes
1 answer
122 views

In what year and in which Bitcoin improvement proposal Opcodes such as OP_MODE have been disabled?

On Bitcoin wiki several opcodes are listed as "disabled". My question is simple: which Bitcoin improvement proposal proposed to disable them, and when they have effectively been disabled in ...
FraMog's user avatar
  • 41
0 votes
1 answer
95 views

The bitcoin opcode seems to have a flat rate

The bitcoin opcode seems to have a flat rate, is that correct? Or, if bitcoin has a price per opcode, please give me the link. If it is a flat rate, please tell me why bitcoin does not have a ...
ground clown's user avatar
2 votes
1 answer
153 views

Are P2SH transactions with disabled opcodes relayed/mined?

Many OPCODES like OP_AND, OP_CAT, OP_SUBSTR are disabled as described in https://en.bitcoin.it/wiki/Script. Although, with Bitcoin Core 0.10.0 Gavin Andresen proposed "any Script" in P2SH ...
Brqoo's user avatar
  • 372
2 votes
1 answer
78 views

How is a locking script reliably detected as a P2PKH script?

I've taken this example from a p2pkh guide: 1976a9145fb0e9755a3424efd2ba0587d20b1e98ee29814a88ac This is broken down into: 19 - byte length of the following unlocking script 76 - OP_DUP: Duplicates ...
Andrej Mitrović's user avatar
1 vote
0 answers
50 views

Why does printing a scriptPubKey have an extra OP_PUSHBYTES_20? [duplicate]

I am building a P2PKH script pubkey in code, and the standard format is: OP_DUP OP_HASH160 <PUBKEYHASH> OP_EQUALVERIFY OP_CHECKSIG However, when I print it (I'm using the bitcoin Rust crate) it ...
Kyle's user avatar
  • 166
3 votes
0 answers
191 views

Which opcodes where disabled by Satoshi Nakamoto for cve 2010 5137

Lot of opcodes where disabled over the years. But which opcodes where disabled Satoshi himself and specifically for the any one can spend any coin bug?
user2284570's user avatar
1 vote
1 answer
160 views

Could CHECKSIGADD be used on new ECDSA multisignatures instead of CHECKMULTISIG?

The proposed Taproot soft fork (BIP 342) defines the new opcode OP_CHECKSIGADD to verify Schnorr multisignatures whilst OP_CHECKMULTISIG (and OP_CHECKMULTISIGVERIFY) are disabled for Taproot spends (...
Michael Folkson's user avatar
2 votes
2 answers
322 views

Given OP_VER was never used, is disabled and not considered useful can its meaning be stripped and it be made OP_SUCCESS?

Given OP_VER (0x62) was never used onchain, is disabled and is not considered useful can its meaning be stripped and it be made OP_SUCCESS for the purposes of introducing a new different opcode in ...
Michael Folkson's user avatar
2 votes
2 answers
151 views

OP_LSHIFT & OP_RSHIFT purpose & functionality

What is the purpose & functionalities of the LSHIFT & RSHIFT Script OP codes ?
Bhala T R's user avatar
1 vote
1 answer
141 views

Bitcoin script verification fails after certain time period

So I want to write a bitcoin script so that after a certain time period (say for example after 30 mins), the verification fails and transaction is marked invalid even if it gets broadcasted. Time ...
Subhra Mazumdar's user avatar
1 vote
2 answers
336 views

Creating a custom transactions

I am currently learning how to create raw transactions. I can already create standard using bitcoin core (0.19.1), but when I wanted to create with custom opcode like this: asm: OP_HASH160 ...
M A's user avatar
  • 89