Chronicle Release
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The Chronicle release is a follow-up of which restored many aspects of the Bitcoin protocol that had been modified in previous software updates, including the removal of most limit-based consensus rules, replacing them with miner configurable settings that give node operators the autonomy needed to set their limits as they determine practical.
The changes introduced in the Chronicle release are detailed in the sections below, outlining the removal of specific restrictions and requirements within the Bitcoin protocol to allow for greater flexibility and configurability for node operators.
To summarize the Chronicle release, the following points should be outlined:
Restoration of Bitcoin's Original Protocol: The Chronicle release aims to restore the original Bitcoin protocol by re-installing specific opcodes and removing listed restrictions, while also balancing stability for businesses that depend on the current state.
Transaction Digest Algorithms: The BSV Blockchain will now support the Original Transaction Digest Algorithm (OTDA), in addition to the current BIP143 digest algorithm, ensuring compatibility and flexibility for developers and users. This restores the original Bitcoin transaction digest algorithm, enabling developers to have greater flexibility in utilizing Bitcoin Script. Usage of the OTDA will require setting the new CHRONICLE [0x20
] sighash flag.
Selective Malleability Restrictions: The Chronicle Release removes restrictions that were put in place to prevent transaction malleability. To address concerns about the reintroduction of sources of transaction malleability, the application of malleability restrictions will depend on the usage of the new CHRONICLE [0x20
] sighash flag. Transactions signed with CHRONICLE enabled will allow relaxed rules, removing strict enforcement of malleability-related constraints. This flexibility is agnostic to the number of signatures in a transaction. The restrictions relevant to the CHRONICLE flag are:
Minimal Encoding Requirement
Low S Requirement for Signatures
NULLFAIL and NULLDUMMY check for OP_CHECKSIG
and OP_CHECKMULTISIG
MINIMALIF Requirement for OP_IF
and OP_NOTIF
Clean Stack Requirement
Data Only in Unlocking Script Requirement
Business Impact and Flexibility: In line with the BSV Blockchain's commitment to stability, existing users and applications using the BIP143 digest (without CHRONICLE) will remain unaffected by the Chronicle update. For developers aiming to leverage the original protocol's behavior, the Chronicle release offers the option to utilize the Original Transaction Digest Algorithm (OTDA) and the flexibility to determine malleability-related restrictions for transactions.
As mentioned above, in the Chronicle release, malleability-related rules are being adjusted dependent on how transactions are signed.
These changes depend on the usage of the new CHRONICLE
[0x20
] Sighash bit. By default, users who do nothing will retain the current behavior (with CHRONICLE
disabled). The OTDA will reintroduce relaxed rules where needed. It is also important to mention that it doesn't matter if the transaction configuration involves multiple signatures within a script or across multiple inputs. This approach enables optional adoption of relaxed malleability constraints. The table below describes all possible scenarios and their expected results:
Single input, single signature
0
BIP143
Strict
Single input, single signature
1
OTDA
Relaxed
Multiple signatures across one or more inputs.
All 0
BIP143
Strict
Multiple signatures across one or more inputs.
All 1
OTDA
Relaxed
Multiple signatures across one or more inputs.
Mixed
Mixed
Strict
Update the script processing so that numbers are not required to be expressed using the minimum number of bytes.
Remove SCRIPT_VERIFY_MINIMALDATA
and associated logic from the software
Remove MinimallyEncoded()
and IsMinimallyEncoded(..)
methods
Remove bsv::MinimallyEncoded()
and bsv::IsMinimallyEncoded(..)
functions.
The configuration parameter maxscriptnumlengthpolicy
limits the size of numbers used in scripts. The default is 10,000 bytes with 0 indicating no external limit.
The maxscriptnumlengthpolicy
configuration parameter default will be changed to unlimited (0).
There are to be no restrictions on the max size of script numbers.
OP_CHECKSIG
and OP_CHECKMULTISIG
RemovalRemove the requirement that if an OP_CHECKSIG
is trying to return a FALSE
value to the stack, that the relevant signature must be an empty byte array. Also remove the requirement that if an OP_CHECKMULTISIG
is trying to return a FALSE
value to the stack, that all signatures passing to this OP_CHECKMULTISIG
must be empty byte arrays.
Remove the requirement that the dummy stack item used in OP_CHECKMULTISIG
is an empty byte array.
The following examples are the combined results of the removal of the LOW_S and NULLFAIL rules.
Notation:
These scripts will return a TRUE
to the stack as before:
These scripts will return a FALSE
to the stack as before:
These scripts that previously failed immediately will return TRUE
under the Chronicle rules:
These scripts that previously failed immediately will return FALSE
under the Chronicle rules:
The input argument to the OP_IF
and OP_NOTIF
opcodes is no longer required to be exactly 1 (the one-byte vector with value 1) to be evaluated as TRUE. Similarly, the input argument to the OP_IF
and OP_NOTIF
opcodes is no longer required to be exactly 0 (the empty vector) to be evaluated as FALSE.
The script engine should not require that the stack has only a single element on it on completion of the execution of a script.
Remove SCRIPT_VERIFY_CLEANSTACK
and associated logic from the software.
The node will no longer require that unlocking scripts only include data and associated pushdata op codes. Functional Opcodes will be permitted.
It should be noted that the unlocking script is evaluated, the resulting main stack is kept, but the conditional and alt stacks are cleared. The locking script is then evaluated. Therefore any OP_RETURN use in the unlocking script simply leads to the end of unlocking script execution - not script execution as a whole.
There are specific use cases for "showing your work" like this in the unlocking script. Typically it is not necessary to include intermediate values, and simply passing the result of any calculation as push data would be sufficient.
The opcodes listed below will be re-instated.
Implementation should exhibit standard behavior. i.e. If the opcode produces an error, the code should immediately return the result of a call to set_error with the appropriate error message and code.
Opcodes do not check if the supplied operands are of the expected type. Rather if an opcode expects a particular data type on top of the stack (tos), it will interpret whatever it finds as that data type.
If an opcode expects values on the stack and they are not present, then an error should be returned.
Opcode number 98 , hex 0x62
OP_VER
pushes the executing transaction’s version onto the stack. The transaction version is the first four bytes of the transaction containing the executing script.
Opcode number 101 , hex 0x65
Compares the tos
with the executing transaction’s version as part of the following traditional if-then-else expression: OP_VERIF [statements] [OP_ELSE [statements]] OP_ENDIF
Logically equivalent to OP_VER OP_IF
.
Opcode number 102, hex 0x66
Compares the tos
with the executing transaction’s version as part of the following expression:
OP_VERNOTIF [statements] [OP_ELSE [statements]] OP_ENDIF
Logically equivalent to OP_VER OP_NOTIF
Originally opcode number 127. Now has value 179, hex 0xb3
Returns substring defined by start index and length.
A zero-length source string generates an error. A negative length generates an error. If the specified length is greater than the source string, the opcode generates an error.
E.g. executing the script below would remove the desired length and start index of the substring.
The string “BSV Blockchain” would be replaced by “Block” on the top of the stack.
Originally opcode number 128. Now has value 180, hex 0xb4
Produces a substring consisting only of the specified number of leftmost characters.
E.g. Executing the script below would leave “BSV” on the top of the stack.
Zero-length strings are allowed.
Originally opcode number 129. Now has value 181, hex 0xb5
Produces a substring consisting only of the specified number of rightmost characters.
E.g. Executing the script below would leave “chain” on the top of the stack.
Zero-length strings are allowed.
Opcode number 141, hex 0x8d
Multiplies the number on the top of the stack by 2.
Opcode number 142, 0x8e
Divides the number on the top of the stack by 2.
Remove the requirement that the signature must be the low “s” value. See
The rest of the Opcodes remain intact; their description can be found in the .