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The Bitcoin developers community is cautious. Implementing a code update is not easy: it requires almost absolute consensus. The Segwit experience has left its mark, and there is no question that a new soft fork will cause so much dissension. Even if Taproot is the improvement of Bitcoin expected by everyone, the implementation process will be long.
Trauma Segwit
Bitcoin is a perfectly inclusive system , but also very elitist . Anyone can clone the Bitcoin code, annotate it, or submit improvements to the whole community ... But it is not enough to come up with a good idea for it to be put into practice!
BIP ( Bitcoin Improvement Proposals ) are carefully analyzed by all developers. The value of Bitcoin lies greatly in the robustness of its code . Each improvement is therefore studied and tested at length , so that it enhances the security of the system, and not vice versa.
This often gives rise to debates by experts… Cryptographers, mathematicians and coders put their paranoia at the service of the network .
Even slight modifications can lead to internal wars in the community. This was particularly the case for Segwit , who divided minds to the point of causing the blockchain to split. It was through this fundamental disagreement over the scalability of Bitcoin that Bitcoin Cash was born.
Segwit: a fratricidal war launched by a few lines of code! -Source
It was a test for the ecosystem, and it is at the edge of this experience that future Bitcoin improvements will be implemented. The consensus must be maximum : in the case of Segwit, 95% of the nodes had to approve the update in order for it to be implemented.
To avoid divisions, the method is different for Taproot . The update is scheduled to be rejected by default after one year if consensus is not reached . If the community validates it, a period of six months is provided to allow developers to plan the terms of its implementation. It will be effective two years later , the maximum deadline for adopting a soft fork at 42 months.
Taproot, what is it?
To understand this improvement in Bitcoin code, one must know how its scripting system works .
To start, Bitcoin allows you to program smart contracts . A Bitcoin transaction is ultimately nothing more than a series of conditional executions, allowing you to move corners from one place to another. The purpose of a smart contract is to take advantage of the non-repudiation of the code to carry out one or more transactions, freely agreed by the stakeholders, without going through a trusted third party .
When you program a transaction on the Bitcoin network, it is transcribed in computer language . No need to delve into its syntax to understand how it works. You just need to have a few notions in mind.
The P2SH system for complex transactions
To carry out one or more transactions on Bitcoin, it is necessary to prove that you are the owner of the coins you wish to move. This is possible thanks to digital signatures . They make it possible to prove to the whole network that one is indeed master of the private key associated with such or such address.
The system is called pay to script hash or P2SH . It allows for complex transactions which may, for example, require several signatures to be validated.
Bitcoin script execution - Source: LearnMeBitcoin.com
Even if P2SH makes it possible to carry out basic smart contracts (series of conditional transactions ), it has a defect .
Indeed, in order to prove the validity of the script, it is necessary to make public all of its content . Whenever bitcoins change hands, their new owner must reveal everything to the network. This has two drawbacks:
- The quantity of data to be published is significant, and it is proportional to the complexity of the transactions to be carried out;
- Making the script public is obviously bad for the confidentiality of the parties involved in the transaction (s). This decreases the level of anonymity of Bitcoin .
MAST (Merkelized Abstract Syntax Trees)
In order to overcome the first problem, cryptographers have an ingenious process .
It rests on the famous Merkle trees . This data structure makes it possible to produce a hash for each execution condition of the script. These hashes are then grouped together in the Merkle tree, which is then chopped in turn. This last hash is called the root of the tree ( Merkle root ).
This then gives a very interesting property to our script. It therefore suffices to make public a single (effective) execution condition so that the entire network can authenticate it .
This already slightly improves Bitcoin's privacy, since the unfulfilled conditions of a script remain private . The network just needs to have the Merkle root and the tree structure ( Merkle path ) to validate the transaction.
MASTs make it possible to considerably lighten the blockchain ... and improve the confidentiality of transactions - Bitcoin Tech Talk .
Schnorr's signatures
Without going into details , this digital signature scheme allows you to aggregate the multiple signatures required for a transaction.
This authentication protocol is also a zero-disclosure proof of knowledge , that is, it is not necessary to know the content of the script in order to prove its authenticity.
Thus, a scripted multi-signature transaction will not be different for the entire network from a single transaction.
Before and after Schnorr - Jamie Redman
Taproot, the ultimate implementation
Taproot combines the data structures of MAST and the signatures of Schnorr .
As we have seen, in order for the Bitcoin network to validate a script, it is sufficient, with MAST , to publish a single execution condition on which the parties agree. The signatures of the parties are aggregated and serve to prove this consensus.
It is therefore necessary with Taproot to create an execution condition which will be signed by the parties to the transaction. It is called " cooperative closure" .
All the other "non-cooperative" execution conditions are then grouped in another script. The latter will be hashed, then used to transform the common public key (resulting from the aggregation of the parties' public keys).
If the conditions for cooperation between the parties are met, it will suffice to publish the script to execute the transaction. Otherwise, it will be necessary to reveal both the script and the original multi-signature to apply the alternative conditions .
Despite the impatience of the community, Taproot will not be implemented anytime soon. This is the consequence of Bitcoin's anti-fragility. As the experiments progress, the organism becomes stronger. The lessons of Segwit have been well assimilated, and the process is now a little longer.
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