This page describes a BIP (Bitcoin Improvement Proposal). BIP: Layer: Consensus (soft fork) Title: Taproot: SegWit version 1 spending rules Author. Process BIPs relate to proposed process changes outside the Bitcoin bonus1xbetsports.websiteational BIPs can be accepted or ignored by the Bitcoin community as it wishes. Bitcoin Improvement Proposal (BIP) Influenced by previous methods of managing open-source code bases supported by distributed teams, such as Python. IS ENGLAND A BETTER PLACE TO LIVE THAN AMERICA
There's also live online events, interactive content, certification prep materials, and more. Start your free trial Appendix B. Bitcoin Improvement Proposals Bitcoin improvement proposals are design documents providing information to the bitcoin community, or describing a new feature for bitcoin or its processes or environment. As per BIP BIP Purpose and Guidelines, there are three kinds of BIP: Standard BIP Describes any change that affects most or all bitcoin implementations, such as a change to the network protocol, a change in block or transaction validity rules, or any change or addition that affects the interoperability of applications using bitcoin.
Informational BIP Describes a bitcoin design issue, or provides general guidelines or information to the bitcoin community, but does not propose a new feature. Informational BIPs do not necessarily represent a bitcoin community consensus or recommendation, so users and implementors may ignore informational BIPs or follow their advice.
Moreover, the depth of a script in the Merkle root leaks information including the minimum depth of the tree, which suggests specific wallet software that created the output and helps clustering. Therefore, the privacy of script spends can be improved by deviating from the optimal tree determined by the probability distribution over the leaves. Just like other existing output types, taproot outputs should never reuse keys, for privacy reasons.
This does not only apply to the particular leaf that was used to spend an output but to all leaves committed to in the output. If leaves were reused, it could happen that spending a different output would reuse the same Merkle branches in the Merkle proof. Using fresh keys implies that taproot output construction does not need to take special measures to randomizing leaf positions because they are already randomized due to the branch-sorting Merkle tree construction used in taproot.
This does not avoid leaking information through the leaf depth and therefore only applies to balanced sub- trees. In addition, every leaf should have a set of keys distinct from every other leaf. The reason for this is to increase leaf entropy and prevent an observer from learning an undisclosed script using brute-force search. Test vectors Test vectors for wallet operation scriptPubKey computation, key path spending, control block construction can be found here.
It consists of two sets of vectors. The first "scriptPubKey" tests concern computing the scriptPubKey and mainnet BIP address given an internal public key, and a script tree. The script tree is encoded as null to represent no scripts, a JSON object to represent a leaf node, or a 2-element array to represent an inner node. The control blocks needed for script path spending are also provided for each of the script leaves.
The second "keyPathSpending" tests consists of a list of test cases, each of which provides an unsigned transaction and the UTXOs it spends. For each of its BIP inputs, the internal private key and the Merkle root it was derived from is given, as well as the expected witness to spend it. All signatures are created with an all-zero 0x In all cases, hexadecimal values represent byte arrays, not numbers.
In particular, that means that provided hash values have the hex digits corresponding to the first bytes first. This differs from the convention used for txids and block hashes, where the hex strings represent numbers, resulting in a reversed order. Validation test vectors used in the Bitcoin Core unit test framework can be found here. Unforgeability of signatures is a necessary requirement to prevent theft.
At least when treating script execution as a digital signature scheme itself, unforgeability can be proven in the Random Oracle Model assuming the Discrete Logarithm problem is hard. A proof for unforgeability of ECDSA in the current script system needs non-standard assumptions on top of that. Note that it is hard in general to model exactly what security for script means, as it depends on the policies and protocols used by wallet software. While typical earlier constructions store a hash of a script or a public key in the output, this is rather wasteful when a public key is always involved.
To guarantee batch verifiability, the public key must be known to every verifier, and thus only revealing its hash as an output would imply adding an additional 32 bytes to the witness. Furthermore, to maintain bit collision security for outputs, a bit hash would be required anyway, which is comparable in size and thus in cost for senders to revealing the public key directly. While the usage of public key hashes is often said to protect against ECDLP breaks or quantum computers, this protection is very weak at best: transactions are not protected while being confirmed, and a very large portion of the currency's supply is not under such protection regardless.
Actual resistance to such systems can be introduced by relying on different cryptographic assumptions, but this proposal focuses on improvements that do not change the security model. Using P2SH-wrapped outputs only provides bit collision security due to the use of a bit hash.
This is considered low, and becomes a security risk whenever the output includes data from more than a single party public keys, hashes, As the control block's initial byte's lowest bit is used to indicate the parity of the public key's Y coordinate, each leaf version needs an even byte value and the immediately following odd byte value that are both not yet used in P2WPKH or P2WSH spending. To indicate the annex, only an "unpaired" available byte is necessary like 0x This choice maximizes the available options for future script versions.
The annex is a reserved space for future extensions, such as indicating the validation costs of computationally expensive new opcodes in a way that is recognizable without knowing the scriptPubKey of the output being spent.
The optimally space-efficient Merkle tree can be constructed based on the probabilities of the scripts in the leaves, using the Huffman algorithm. As that is our security bound, scripts that truly have such a low chance can probably be removed entirely. In addition, in order to support some forms of static analysis that rely on being able to identify script spends without access to the output being spent, it is recommended to avoid using any leaf versions that would conflict with a valid first byte of either a valid P2WPKH pubkey or a valid P2WSH script that is, both v and v 1 should be an undefined, invalid or disabled opcode or an opcode that is not valid as the first opcode.
The values that comply to this rule are the 32 even values between 0xc0 and 0xfe and also 0x66, 0x7e, 0x80, 0x84, 0x96, 0x98, 0xba, 0xbc, 0xbe. Note also that this constraint implies that leaf versions should be shared amongst different witness versions, as knowing the witness version requires access to the output being spent.
This is possible because we do not actually care about the position of specific scripts in the tree; only that they are actually committed to. The chosen construction does require two invocations of the SHA compression functions, one of which can be avoided in theory see BIP However, it seems preferable to stick to constructions that can be implemented using standard cryptographic primitives, both for implementation simplicity and analyzability.
If necessary, a significant part of the second compression function can be optimized out by specialization for byte inputs. The parity of the Y coordinate is necessary to lift the X coordinate q to a unique point. While this is not strictly necessary for verifying the taproot commitment as described above, it is necessary to allow batch verification. Alternatively, Q could be forced to have an even Y coordinate, but that would require retrying with different internal public keys or different messages until Q has that property.
There is no downside to adding the parity bit because otherwise the control block bit would be unused. BIP specifies validity rules that apply for leaf version 0xc0, but future proposals can introduce rules for other leaf versions. By doing so, it is easier to reason about the worst case amount of signature hashing an implementation with adequate caching must perform. Hashes that go into the signature message and the message itself are now computed with a single SHA invocation instead of double SHA There is no expected security improvement by doubling SHA because this only protects against length-extension attacks against SHA which are not a concern for signature messages because there is no secret data.
Therefore doubling SHA is a waste of resources.
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Given that the blockchain is software, think about BIPs as software updates. Because Bitcoin doesn't have centralized leadership, BIPs make it possible for the community to communicate ideas, draft and propose technical changes and eventually vote on accepting or opposing the proposal.
The proposals and discussions are available or anyone to see on GitHub , which is a popular open-source platform among software developers. Who can submit a BIP? Theoretically, anyone can suggest an upgrade and flesh it out as a BIP, because Bitcoin is an open-source, decentralized network.
Champions convert the idea into detailed technical documentation according to the BIP standards. Then, the BIP champion submits the proposal to the BIP editor, who acts as an auditor of the proposal and is responsible for its administration. The editor can request revisions from the author or even reject it.
If the editor says the proposal is ready to proceed, it gets an official number for example, BIP and the champion presents the BIP to the community. The BIP has to go through different stages before it can be implemented. Proposed: The BIP includes a plan on how to implement the change in the blockchain. Final: The BIP is accepted and ready to be implemented. Implementation consists of two steps.
First, the upgrade has to be merged into the blockchain's software code Bitcoin Core , then it has to be activated. The Taproot upgrade, for example, was merged in October and activated in November In the background, if the BIP necessitates code changes to Bitcoin Core, developers will work on writing, testing, and integrating that code. If legitimate arguments are raised by a significant portion of users, the BIP will likely be withdrawn or rejected, and the proposal process must be abandoned or restarted.
If the community achieves rough consensus, and no legitimate drawbacks of the proposal are found, the community will choose an activation path and begin activating the BIP. This process takes different forms depending on the type of BIP at hand. Others propose community standards, which are suggestions meant to encourage interoperability of different Bitcoin related software.
Finally, some BIPs propose process guidelines. Each BIP type is treated and activated differently. Consensus BIPs Bitcoin is a network governed by rules. These rules are independently enforced by tens of thousands of Bitcoin nodes, who must all establish consensus by following the same rules. If half of Bitcoin nodes follow one rule set and the other half follow a different rule set, the network would fracture.
Consensus BIPs are carefully constructed to remain backwards compatible to the greatest extent possible. This allows old nodes that choose not to upgrade to remain full members of the network. Consensus changes require explicit activation on the Bitcoin network. Several process BIPs exist which define possible activation paths for consensus changes. These BIPs might propose encoding schemes or best practices for securing bitcoin.
Since Bitcoin is an open system, every software provider can choose whether or not they will adopt these standards. Some standards require universal adoption in order to guarantee interoperability. For example, a wallet which cannot interpret a Bitcoin address will be completely useless, and a wallet which uses different address formats from the rest of the Bitcoin community will lose money for its users. In fact, mnemonic backup phrases as defined in BIP 39 have been adopted by many wallet providers, but are not used by Bitcoin Core itself.
Although this lack of universal adoption is inconvenient, it does not eliminate the utility or security of the software.
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