# 20 - Dash Opcode Updates 
DIP: 0020
Title: Dash Opcode Updates
Author: Mart Mangus
Comments: https://github.com/Dash-Dev-EE/DIP-draft/issues
Status: Draft
Layer: Consensus (hard fork)
Created: 2020-06-01
License: MIT License
# Abstract This DIP describes reactivation of several disabled opcodes (`OP_CAT`, `OP_AND`, `OP_OR`, `OP_XOR`, `OP_DIV`, `OP_MOD`) and activation of several new opcodes (`OP_SPLIT`, `OP_BIN2NUM`, `OP_NUM2BIN`, `OP_CHECKDATASIG` and `OP_CHECKDATASIGVERIFY`) to expand the use of the Dash scripting system. # Motivation Several opcodes were disabled in the Bitcoin scripting system due to the discovery of a series of bugs in the early days of Bitcoin. The functionality of these opcodes was re-examined by Bitcoin Cash developers few years ago. Many of the disabled opcodes have been enabled and several of them re-designed to replace the original ones. In addition, several new opcodes have been written and implemented to further improve the Bitcoin scripting system in Bitcoin Cash. Implementing these opcodes into Dash is necessary for broadening the functionality of the system and enabling developers to build new solutions, which in turn would expand the use of Dash. # Specification |Word |OpCode |Hex |Input |Output | Description | |----------------------|-------|----|------|--------|-------------------------------------------------------| |OP_CAT |126 |0x7e|x1 x2 |out |Concatenates two byte arrays | |OP_SPLIT |127 |0x7f|x n |x1 x2 |Split byte array *x* at position *n* | |OP_NUM2BIN |128 |0x80|a b |out |Convert numeric *a* into byte array of length *b* | |OP_BIN2NUM |129 |0x81|x |out |Convert byte array *x* into numeric | |OP_AND |132 |0x84|x1 x2 |out |Boolean *AND* between each bit of the inputs | |OP_OR |133 |0x85|x1 x2 |out |Boolean *OR* between each bit of the inputs | |OP_XOR |134 |0x86|x1 x2 |out |Boolean *EXCLUSIVE OR* between each bit of the inputs | |OP_DIV |150 |0x96|a b |out |*a* is divided by *b* | |OP_MOD |151 |0x97|a b |out |return the remainder after *a* is divided by *b* | |OP_CHECKDATASIG |186 |0xba|sig msg pk|out |If signature *sig* is valid, output to the stack| |OP_CHECKDATASIGVERIFY |187 |0xbb|sig msg pk|- |If signature *sig* is valid, false will cause the script to fail| ## OP_CAT Opcode (decimal): 126 Opcode (hex): 0x7e `OP_CAT` takes two byte arrays from the stack, concatenates them and pushes the result back to the stack. x1 x2 OP_CAT → out Example: * `0x11 0x2233 OP_CAT → 0x112233` References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_cat) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1097) ## OP_SPLIT Opcode (decimal): 127 Opcode (hex): 0x7f `OP_SPLIT` is the inverse of `OP_CAT` and a replacement operation for disabled opcodes `OP_SUBSTR`, `OP_LEFT` and `OP_RIGHT`. `OP_SPLIT` takes a byte array, splits it at the position `n` (a number) and returns two byte arrays. x n OP_SPLIT → x1 x2 Examples: * `0x001122 0 OP_SPLIT → OP_0 0x001122` * `0x001122 1 OP_SPLIT → 0x00 0x1122` * `0x001122 2 OP_SPLIT → 0x0011 0x22` * `0x001122 3 OP_SPLIT → 0x001122 OP_0` References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_split) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1099) ## OP_NUM2BIN Opcode (decimal): 128 Opcode (hex): 0x80 `OP_NUM2BIN` converts numeric value `n` to a byte array of length `m`. n m OP_NUM2BIN → x Examples: * `0x02 4 OP_NUM2BIN → 0x00000002` * `0x85 4 OP_NUM2BIN → 0x80000005` References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_num2bin) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1222) ## OP_BIN2NUM Opcode (decimal): 129 Opcode (hex): 0x81 `OP_BIN2NUM` converts byte array value `x` into a numeric value. x1 OP_BIN2NUM → n if `x1` is any form of zero, including negative zero, then `OP_0` must be the result. Examples: * `0x0000000002 OP_BIN2NUM → 0x02` * `0x800005 OP_BIN2NUM → 0x85` References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_bin2num) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1220) ## OP_AND Opcode (decimal): 132 Opcode (hex): 0x84 Boolean *and* between each bit in the operands. x1 x2 OP_AND → out References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_and) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1211) ## OP_OR Opcode (decimal): 133 Opcode (hex): 0x85 Boolean *or* between each bit in the operands. x1 x2 OP_OR → out References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_or) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1211) ## OP_XOR Opcode (decimal): 134 Opcode (hex): 0x86 Boolean *xor* between each bit in the operands. x1 x2 OP_XOR → out References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_xor) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1211) ## OP_DIV Opcode (decimal): 150 Opcode (hex): 0x96 Return the integer quotient of `a` and `b`. If the result would be a non-integer it is rounded *towards* zero. `a` and `b` are interpreted as numeric values. a b OP_DIV → out References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_div) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1212) ## OP_MOD Opcode (decimal): 151 Opcode (hex): 0x97 Returns the remainder after dividing `a` by `b`. The output will be represented using the least number of bytes required. `a` and `b` are interpreted as numeric values. a b OP_MOD → out References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-reenabled-opcodes.md#op_mod) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1212) ## OP_CHECKDATASIG Opcode (decimal): 186 Opcode (hex): 0xba `OP_CHECKDATASIG` checks whether a signature is valid with respect to a message and a public key. It allows Script to validate arbitrary messages from outside the blockchain. sig msg pubKey OP_CHECKDATASIG → out If the stack is well formed, then `OP_CHECKDATASIG` pops the top three elements [`sig`, `msg`, `pubKey`] from the stack and pushes true onto the stack if `sig` is valid with respect to the raw single-SHA256 hash of `msg` and `pubKey` using the secp256k1 elliptic curve. Otherwise, it pops three elements and pushes false onto the stack in the case that `sig` is the empty string and fails in all other cases. References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/op_checkdatasig.md#op_checkdatasig-specification) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1621) * Implementation updates: [1](https://reviews.bitcoinabc.org/D1646), [2](https://reviews.bitcoinabc.org/D1653), [3](https://reviews.bitcoinabc.org/D1666) ## OP_CHECKDATASIGVERIFY Opcode (decimal): 187 Opcode (hex): 0xbb `OP_CHECKDATASIGVERIFY` is equivalent to `OP_CHECKDATASIG` followed by `OP_VERIFY`. It leaves nothing on the stack and will cause the script to fail immediately if the signature check does not pass. sig msg pubKey OP_CHECKDATASIGVERIFY References: * [Detailed specification in Bitcoin Cash](https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/op_checkdatasig.md#op_checkdatasigverify-specification) * [Implementation in Bitcoin ABC](https://reviews.bitcoinabc.org/D1621) * Implementation updates: [1](https://reviews.bitcoinabc.org/D1646), [2](https://reviews.bitcoinabc.org/D1653), [3](https://reviews.bitcoinabc.org/D1666) # Compatibility This change will be a hard-fork to the protocol and older software has to be updated to continue to operate. # References * Bitcoin Cash specification of restored disabled opcodes: * Bitcoin Cash specification of OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY: * Bitcoin Cash OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY implementation: * * * * * Bitcoin Cash OP_CAT implementation: * Bitcoin Cash OP_SPLIT implementation: * Bitcoin Cash OP_BIN2NUM implementation: * Bitcoin Cash OP_NUM2BIN implementation: * Bitcoin Cash OP_AND, OP_OR and OP_XOR implementation: * Bitcoin Cash OP_DIV and OP_MOD implementation: # Copyright This document is licensed under the [MIT License](https://opensource.org/licenses/MIT).