From 6943941c23a0c30a648972b41443faf3215d7848 Mon Sep 17 00:00:00 2001 From: Steven Roose Date: Wed, 13 Dec 2023 13:01:11 +0000 Subject: [PATCH] fixup try fix mediawiki rendering without an online renderer tool --- bip-txhash.mediawiki | 263 ++++++++++++++++++++++--------------------- 1 file changed, 132 insertions(+), 131 deletions(-) diff --git a/bip-txhash.mediawiki b/bip-txhash.mediawiki index e9765d834d..94e487965d 100644 --- a/bip-txhash.mediawiki +++ b/bip-txhash.mediawiki @@ -34,11 +34,11 @@ OP_CHECKTXHASHVERIFY does the following: * There is at least one element on the stack, fail otherwise. * The element on the stack is at least 32 bytes long, fail otherwise. * The first 32 bytes are interpreted as the TxHash and the remaining suffix - bytes specify the TxFieldSelector. +bytes specify the TxFieldSelector. * If the TxFieldSelector is invalid, fail. * The actual TxHash of the transaction at the current input index, calculated - using the given TxFieldSelector must be equal to the first 32 bytes of the - element on the stack, fail otherwise. +using the given TxFieldSelector must be equal to the first 32 bytes of the +element on the stack, fail otherwise. OP_TXHASH uses tapscript opcode OP_SUCCESS189 (0xbd) as a soft fork upgrade. @@ -49,113 +49,114 @@ OP_TXHASH does the following: * The element is interpreted as the TxFieldSelector and is popped off the stack. * If the TxFieldSelector is invalid, fail. * The 32-byte TxHash of the transaction at the current input index, - calculated using the given TxFieldSelector is pushed onto the stack. +calculated using the given TxFieldSelector is pushed onto the stack. The TxFieldSelector has the following semantics. We will give a brief conceptual summary, followed by a reference implementation of the CalculateTxHash function. * There are two special cases for the TxFieldSelector: - - the empty value, zero bytes long: it is set equal to TXFS_SPECIAL_TEMPLATE, - the de-facto default value which means everything except the prevouts and - the prevout scriptPubkeys. - TXFS_SPECIAL_TEMPLATE is 4 bytes long, as follows: - 1. TXFS_ALL - 2. TXFS_INPUTS_TEMPLATE | TXFS_OUTPUTS_ALL - 3. TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL - 4. TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL - - the 0x00 byte: it is set equal to TXFS_SPECIAL_ALL, which means "ALL" - and is primarily useful to emulate SIGHASH_ALL when OP_TXHASH is used in - combination with OP_CHECKSIGFROMSTACK. - TXFS_SPECIAL_TEMPLATE is 4 bytes long, as follows: - 1. TXFS_ALL - 2. TXFS_INPUTS_ALL | TXFS_OUTPUTS_ALL - 3. TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL - 4. TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL +** the empty value, zero bytes long: it is set equal to TXFS_SPECIAL_TEMPLATE, +the de-facto default value which means everything except the prevouts and +the prevout scriptPubkeys. +TXFS_SPECIAL_TEMPLATE is 4 bytes long, as follows: +# TXFS_ALL +# TXFS_INPUTS_TEMPLATE | TXFS_OUTPUTS_ALL +# TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL +# TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL +** the 0x00 byte: it is set equal to TXFS_SPECIAL_ALL, which means "ALL" +and is primarily useful to emulate SIGHASH_ALL when OP_TXHASH is used in +combination with OP_CHECKSIGFROMSTACK. +TXFS_SPECIAL_TEMPLATE is 4 bytes long, as follows: +# TXFS_ALL +# TXFS_INPUTS_ALL | TXFS_OUTPUTS_ALL +# TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL +# TXFS_INOUT_NUMBER | TXFS_INOUT_SELECTION_ALL * The first byte of the TxFieldSelector has its 8 bits assigned as follows, - from lowest to highest: - 1. version (TXFS_VERSION) - 2. locktime (TXFS_LOCKTIME) - 3. current input index (TXFS_CURRENT_INPUT_IDX) - 4. current input control block (or empty) (TXFS_CURRENT_INPUT_CONTROL_BLOCK) - 5. current script last OP_CODESEPARATOR position (or 0xffffffff) - (TXFS_CURRENT_INPUT_LAST_CODESEPARATOR_POS) - 6. inputs (TXFS_INPUTS) - 7. outputs (TXFS_OUTPUTS) +from lowest to highest: +# version (TXFS_VERSION) +# locktime (TXFS_LOCKTIME) +# current input index (TXFS_CURRENT_INPUT_IDX) +# current input control block (or empty) (TXFS_CURRENT_INPUT_CONTROL_BLOCK) +# current script last OP_CODESEPARATOR position (or 0xffffffff) (TXFS_CURRENT_INPUT_LAST_CODESEPARATOR_POS) +# inputs (TXFS_INPUTS) +# outputs (TXFS_OUTPUTS) * The last (highest) bit of the first byte (TXFS_CONTROL), we will call the - "control bit", and it can be used to control the behavior of the opcode. For - OP_TXHASH and OP_CHECKTXHASHVERIFY, the control bit is used to determine - whether the TxFieldSelector itself has to be included in the resulting hash. - (For potential other uses of the TxFieldSelector (like a hypothetical OP_TX), - this bit can be repurposed.) +"control bit", and it can be used to control the behavior of the opcode. For +OP_TXHASH and OP_CHECKTXHASHVERIFY, the control bit is used to determine +whether the TxFieldSelector itself has to be included in the resulting hash. +(For potential other uses of the TxFieldSelector (like a hypothetical OP_TX), +this bit can be repurposed.) * If either "inputs" or "outputs" is set to 1, expect another byte with its 8 - bits assigning the following variables, from lowest to highest: - * Specifying which fields of the inputs will be selected: - 1. prevouts (TXFS_INPUTS_PREVOUTS) - 2. sequences (TXFS_INPUTS_SEQUENCES) - 3. scriptSigs (TXFS_INPUTS_SCRIPTSIGS) - 4. prevout scriptPubkeys (TXFS_INPUTS_PREV_SCRIPTPUBKEYS) - 5. prevout values (TXFS_INPUTS_PREV_VALUED) - 6. taproot annexes (TXFS_INPUTS_TAPROOT_ANNEXES) - * Specifying which fields of the outputs will be selected: - 7. scriptPubkeys (TXFS_OUTPUTS_SCRIPTPUBKEYS) - 8. values (TXFS_OUTPUTS_VALUES) +bits assigning the following variables, from lowest to highest: +** Specifying which fields of the inputs will be selected: +# prevouts (TXFS_INPUTS_PREVOUTS) +# sequences (TXFS_INPUTS_SEQUENCES) +# scriptSigs (TXFS_INPUTS_SCRIPTSIGS) +# prevout scriptPubkeys (TXFS_INPUTS_PREV_SCRIPTPUBKEYS) +# prevout values (TXFS_INPUTS_PREV_VALUED) +# taproot annexes (TXFS_INPUTS_TAPROOT_ANNEXES) +** Specifying which fields of the outputs will be selected: +# scriptPubkeys (TXFS_OUTPUTS_SCRIPTPUBKEYS) +# values (TXFS_OUTPUTS_VALUES) + +//TODO(stevenroose) check that the 7 and 8 render correctly * We define as follows: - - TXFS_ALL = TXFS_VERSION | TXFS_LOCKTIME | TXFS_CURRENT_INPUT_IDX | TXFS_CURRENT_INPUT_CONTROL_BLOCK - | TXFS_CURRENT_INPUT_LAST_CODESEPARATOR_POS | TXFS_INPUTS | TXFS_OUTPUTS | TXFS_CONTROL - - TXFS_INPUTS_ALL = TXFS_INPUTS_PREVOUTS | TXFS_INPUTS_SEQUENCES | TXFS_INPUTS_SCRIPTSIGS - | TXFS_INPUTS_PREV_SCRIPTPUBKEYS | TXFS_INPUTS_PREV_VALUES | TXFS_INPUTS_TAPROOT_ANNEXES - - TXFS_INPUTS_TEMPLATE = TXFS_INPUTS_SEQUENCES | TXFS_INPUTS_SCRIPTSIGS | TXFS_INPUTS_PREV_VALUES - | TXFS_INPUTS_TAPROOT_ANNEXES - - TXFS_OUTPUTS_ALL = TXFS_OUTPUTS_SCRIPTPUBKEYS | TXFS_OUTPUTS_VALUES +** TXFS_ALL = TXFS_VERSION | TXFS_LOCKTIME | TXFS_CURRENT_INPUT_IDX | TXFS_CURRENT_INPUT_CONTROL_BLOCK +| TXFS_CURRENT_INPUT_LAST_CODESEPARATOR_POS | TXFS_INPUTS | TXFS_OUTPUTS | TXFS_CONTROL +** TXFS_INPUTS_ALL = TXFS_INPUTS_PREVOUTS | TXFS_INPUTS_SEQUENCES | TXFS_INPUTS_SCRIPTSIGS +| TXFS_INPUTS_PREV_SCRIPTPUBKEYS | TXFS_INPUTS_PREV_VALUES | TXFS_INPUTS_TAPROOT_ANNEXES +** TXFS_INPUTS_TEMPLATE = TXFS_INPUTS_SEQUENCES | TXFS_INPUTS_SCRIPTSIGS | TXFS_INPUTS_PREV_VALUES +| TXFS_INPUTS_TAPROOT_ANNEXES +** TXFS_OUTPUTS_ALL = TXFS_OUTPUTS_SCRIPTPUBKEYS | TXFS_OUTPUTS_VALUES For both inputs and then outputs, do the following: * If the "in/outputs" field is set to 1, another additional byte is expected: - * The highest bit (TXFS_INOUT_NUMBER) indicates whether the "number of - in-/outputs" should be committed to. - * For the remaining bits, there are three exceptional values: - - 0x00 (TXFS_INOUT_SELECTION_NONE) means "no in/outputs" - (hence only the number of them as 0x80 (TXFS_INOUT_NUMBER)). - - 0x40 (TXFS_INOUT_SELECTION_CURRENT) means "select only the in/output of - the current input index" (it is invalid when current index exceeds number - of outputs). - - 0x3f (TXFS_INOUT_SELECTION_ALL) means "select all in/outputs". - * The second highest bit (TXFS_INOUT_SELECTION_MODE) is the "specification mode": - - Set to 0 it means "leading mode". - - Set to 1 it means "individual mode". - * The third highest bit (TXFS_INOUT_SELECTION_SIZE) is used to indicate the - "index size", i.e. the number of bytes will be used to represent in/output - indices. - * In "leading mode", - - With "index size" set to 0, the remaining lowest 5 bits of the first byte - will be interpreted as the number of leading in/outputs to select. - - With "index size" set to 1, the remaining lowest 5 bits of the first byte - together with the 8 bits of the next byte will be interpreted as the - number of leading in/outputs to select. - * In "individual mode", the remaining lowest 5 bits of the first byte will be - interpreted as `n`, the number of individual in/outputs to select. - - With "index size" set to 0, interpret the following `n` individual bytes - as the indices of an individual in/outputs to select. - - With "index size" set to 1, interpret the next `n` pairs of two bytes as - the indices of individual in/outputs to select. +** The highest bit (TXFS_INOUT_NUMBER) indicates whether the "number of +in-/outputs" should be committed to. +** For the remaining bits, there are three exceptional values: +*** 0x00 (TXFS_INOUT_SELECTION_NONE) means "no in/outputs" +(hence only the number of them as 0x80 (TXFS_INOUT_NUMBER)). +*** 0x40 (TXFS_INOUT_SELECTION_CURRENT) means "select only the in/output of +the current input index" (it is invalid when current index exceeds number +of outputs). +*** 0x3f (TXFS_INOUT_SELECTION_ALL) means "select all in/outputs". +** The second highest bit (TXFS_INOUT_SELECTION_MODE) is the "specification mode": +*** Set to 0 it means "leading mode". +*** Set to 1 it means "individual mode". +** The third highest bit (TXFS_INOUT_SELECTION_SIZE) is used to indicate the +"index size", i.e. the number of bytes will be used to represent in/output +indices. +** In "leading mode", +*** With "index size" set to 0, the remaining lowest 5 bits of the first byte +will be interpreted as the number of leading in/outputs to select. +*** With "index size" set to 1, the remaining lowest 5 bits of the first byte +together with the 8 bits of the next byte will be interpreted as the +number of leading in/outputs to select. +** In "individual mode", the remaining lowest 5 bits of the first byte will be +interpreted as `n`, the number of individual in/outputs to select. +*** With "index size" set to 0, interpret the following `n` individual bytes +as the indices of an individual in/outputs to select. +*** With "index size" set to 1, interpret the next `n` pairs of two bytes as +the indices of individual in/outputs to select. Effectively, this allows a user to select -- all in/outputs -- the current input index -- the leading in/outputs up to 8192 -- up to 32 individually selected in/outputs +* all in/outputs +* the current input index +* the leading in/outputs up to 8192 +* up to 32 individually selected in/outputs The TxFieldSelector is invalid when -- a byte is expected but missing -- additional unexpected bytes are present -- index size is set to 1 while not being necessary -- a leading number of individual index is selected out of bounds of the in/outputs -- individual indices are duplicated or not in increasing order +* a byte is expected but missing +* additional unexpected bytes are present +* index size is set to 1 while not being necessary +* a leading number of individual index is selected out of bounds of the in/outputs +* individual indices are duplicated or not in increasing order These limitations are to avoid potential TxFieldSelector malleability. It is however allowed to use leading mode where it could be "all". This @@ -166,33 +167,33 @@ is important to allow for optional addition of extra inputs or outputs. ===Resource limits=== * For legacy scripts and segwit, we don't add any extra resource limitations, - with the argumentation that OP_CHECKTXHASHVERIFY already requires the user to - provide at least 32 bytes of extra transaction size, either in the input - scriptSig, or the witness. Additional more complex hashes require additional - witness bytes. Given that OP_CAT is not available in this context, if a - malicious user tries to increase the number of TransactionHashes being - calculated by using opcodes like OP_DUP, the TxFieldSelector for all these - calculations is identical, so the calculation can be cached within the same - transaction. +with the argumentation that OP_CHECKTXHASHVERIFY already requires the user to +provide at least 32 bytes of extra transaction size, either in the input +scriptSig, or the witness. Additional more complex hashes require additional +witness bytes. Given that OP_CAT is not available in this context, if a +malicious user tries to increase the number of TransactionHashes being +calculated by using opcodes like OP_DUP, the TxFieldSelector for all these +calculations is identical, so the calculation can be cached within the same +transaction. * For tapscript, primarily motivated by the cheaper opcode OP_TXHASH (it - doesn't require an additional 32 witness bytes be provided) and the potential - future addition of byte manipulation opcodes like OP_CAT, an additional cost - is specified per TransactionHash execution. - Using the same validation budget ("sigops budget") introduced in BIP-0342, - each TransactionHash decreases the validation budget by 10. - If this brings the budget below zero, the script fails immediately. +doesn't require an additional 32 witness bytes be provided) and the potential +future addition of byte manipulation opcodes like OP_CAT, an additional cost +is specified per TransactionHash execution. +Using the same validation budget ("sigops budget") introduced in BIP-0342, +each TransactionHash decreases the validation budget by 10. +If this brings the budget below zero, the script fails immediately. - The following considerations should be made: +The following considerations should be made: - * All fields that can be of arbitrary size are cachable as TransactionHash - always hashes their hashed values. - * In "individual mode", a user can at most commit 32 inputs or outputs, which we - don't consider excessive for potential repeated use. - * In "prefix mode", a caching strategy can be used where the SHA256 context is - stored every N in/outputs so that multiple executions of the TransactionHash - function can use the caches and only have to hash an additional N-1 items at - most. +** All fields that can be of arbitrary size are cachable as TransactionHash +always hashes their hashed values. +** In "individual mode", a user can at most commit 32 inputs or outputs, which we +don't consider excessive for potential repeated use. +** In "prefix mode", a caching strategy can be used where the SHA256 context is +stored every N in/outputs so that multiple executions of the TransactionHash +function can use the caches and only have to hash an additional N-1 items at +most. ==Motivation== @@ -204,33 +205,33 @@ constraints on transactions. Additionally, the constructions specified in this BIP can lay the groundwork for some potential future upgrades: * The TxFieldSelector construction would work well with a hypothetical opcode - OP_TX that allows for directly introspecting the transaction by putting the - fields selected on the stack instead of hashing them together. +OP_TX that allows for directly introspecting the transaction by putting the +fields selected on the stack instead of hashing them together. * The TransactionHash obtained by OP_TXHASH can be combined with a hypothetical - opcode OP_CHECKSIGFROMSTACK to effectively create an incredibly flexible - signature hash, which would enable constructions like SIGHASH_ANYPREVOUT. +opcode OP_CHECKSIGFROMSTACK to effectively create an incredibly flexible +signature hash, which would enable constructions like SIGHASH_ANYPREVOUT. ===Comparing with some alternative proposals=== * This proposal strictly generalizes BIP-119's OP_CHECKTEMPLATEVERIFY, as the - default mode of our TxFieldSelector is effectively the same (though not - byte-for-byte identical) as what OP_CTV acomplishes, without costing any - additional bytes. Additionally, using OP_CHECKTXHASHVERIFY allows for more - flexibility which can help in the case for - * enabling adding fees to a transaction without breaking a multi-tx protocol; - * multi-user protocols where users are only concerned about their own inputs - and outputs. +default mode of our TxFieldSelector is effectively the same (though not +byte-for-byte identical) as what OP_CTV acomplishes, without costing any +additional bytes. Additionally, using OP_CHECKTXHASHVERIFY allows for more +flexibility which can help in the case for +** enabling adding fees to a transaction without breaking a multi-tx protocol; +** multi-user protocols where users are only concerned about their own inputs +and outputs. * Constructions like OP_IN_OUT_VALUE used with OP_EQUALVERIFY can be emulated by - two OP_TXHASH instances by using the TxFieldSelector to select a single input - value first and a single output value second and enforcing equality on the - hashes. Neither of these alternatives can be used to enforce small value - differencials without the use of 64-bit arithmetic. +two OP_TXHASH instances by using the TxFieldSelector to select a single input +value first and a single output value second and enforcing equality on the +hashes. Neither of these alternatives can be used to enforce small value +differencials without the use of 64-bit arithmetic. * Like mentioned above, SIGHASH_ANYPREVOUT can be emulated using OP_TXHASH when - combined with OP_CHECKSIGFROMSTACK: - ` OP_TXHASH OP_CHECKSIGFROMSTACK` effectively emulates - SIGHASH_ANYPREVOUT. +combined with OP_CHECKSIGFROMSTACK: +` OP_TXHASH OP_CHECKSIGFROMSTACK` effectively emulates +SIGHASH_ANYPREVOUT. @@ -245,9 +246,9 @@ implementation. ==Implementation== * A proposed implementation for Bitcoin Core is available here: - https://github.com/bitcoin/bitcoin/pull/29050 +https://github.com/bitcoin/bitcoin/pull/29050 * A proposed implementation for rust-bitcoin is available here: - https://github.com/rust-bitcoin/rust-bitcoin/pull/2275 +https://github.com/rust-bitcoin/rust-bitcoin/pull/2275 ==Acknowledgement==