"For the moon!"

Although this crypto-currency rallying cry is usually used when the price of a coin starts to climb, this time the slogan is used to demonstrate its enthusiasm for the progress made on an expected bitcoin code optimization since a long time.

Called Schnorr signatures, this technology seeks to replace the existing Bitcoin signature scheme with a schema that overwrites the signature data. The concept is so appealing in part because it frees up space in the blockchain, which should help solve both the transaction latency and the high fees that Bitcoin users sometimes have to endure.

According to developers working on technology, the change would result in a 25-30% increase in Bitcoin's trading capacity.

Yannick Seurin, a cryptographer from the French cybersecurity agency ANSSI, who works on cryptography behind Schnorr, told CoinDesk:

"The Schnorr signatures and the applications that allow them to generate high hopes, as evidenced by the recent debate on the scale, any improvement in efficiency is very beneficial for bitcoin . "

Indeed, the bitcoin community is united around several technologies to make bitcoin more efficient, and as such, cheaper, faster and easier to use for payments. Schnorr is only one of them, joining the FIBER network, the peer-to-peer optimizations and, most ambitious of all, the future Lightning Network.

But Schnorr has recently become the focus of some of Bitcoin's most renowned developers.

This is due not only to the fact that SegWit is enabled on Bitcoin (a technology supported by Schnorr), but also to the other benefits offered by Schnorr signatures, such as improving privacy on certain types of transactions and the reduction of spam. the network.

Jonas Nick, for example, told CoinDesk that he was interested in the benefits of confidentiality, no surprise for the security engineer at Blockstream's infrastructure. Still, he is also attracted by the way he could work with other code changes to unlock more advanced bitcoin use cases.

"I am particularly excited by the idea that smart contracts look like normal chain payments, with Schnorr, MAST, Taproot and Graftroot signatures," said Nick, referring to a number of changes. . oriented towards the improvement of smart bitcoin contracts.

Subtle attacks

The excitement sparked by Schnorr does not date from yesterday – technology has been in development since 2012.

Although this may seem odd to some, for those who are close to technology, these delays will not be surprising. First, there are not many developers who know bitcoin and cryptography well enough to help with a change such as Schnorr.

And secondly, since Schnorr would be a big change for the bitcoin network of more than 100 billion dollars, the technology needs a review and a peer test.

Both certainly slowed Schnorr's progress.

According to famous Bitcoin collaborator and Blockstream co-founder, Pieter Wuille, at a conference at Stanford, Schnorr has addressed several "non-obvious challenges" over the years.

For example, last year Wuille and other developers found a "malicious attack" in their implementation of Schnorr, causing them to submit a document describing a possible solution. But, the academic committee to which the document was submitted, categorically rejected it, indicating a better document – although unrelated to bitcoin – that was already dealing with the attack vector in a more safe.

And so is the Seurin cryptographer from ANSSI involved with the bitcoin developers.

"I noticed that the specific signature aggregation system they thought did not have adequate security analysis at that time," he said. said. "As a provable security is my specific area of ​​research, and I've already worked on Schnorr's signatures, I contacted Pieter Wuille."

Wuille then sent the paper to Seurin, and with Bitcoin contributor Core Gregory Maxwell and Blockstream mathematician Andrew Poelstra, wrote a safer construction.

And while this construction helped, another problem appeared a little later.

Another attack vector was found by Blockstream's Russell engineer O & # 39; Connor (Wuille nicknamed him "Russell's attack"), which would allow users to steal bitcoin that has been treated with the signature theme.

In the presentation, Wuille said:

"So something to learn about this, at least for myself, is that the attack models in multiparty systems can be very subtle, it was not at all obvious."

Process and Politics

These attack vectors are solved, but work on the technology continues.

Several Bitcoin improvement proposals (BIPs) are in preparation, Wuille said at a conference. And once these are completed, it will provide blueprints for how the new signing system works and how exactly it would be added to bitcoin. In addition, other bitcoin contributors will then have a chance to review and propose changes to the implementations.

Not to mention that the implementation of a code is long, which, according to Nick, has been a fuzz test for a while. The Fuzz test refers to throwing random data on a piece of code and checking if the output is still correct.

"Since you're doing hundreds of times a second on many hearts for a long time, [fuzz testing] has historically proven itself by finding subtle bugs," Nick told CoinDesk, adding:

"We have not found a problem … while strengthening our confidence in implementation."

If this remains the case, Schnorr's code should not take so long, according to Wuille.

In his speech, Wuille said, "By ignoring the policy, it's not that difficult to add an opcode with the help of SegWit scripting."

Yet, as the controversy surrounding the SegWit activation posted, the policy could be a hard thing to ignore.

Anyway, the code change has attracted a lot of attention recently, developers have written explanatory articles on the blog and a number of people have talked about it on Reddit.

But, with billions of dollars at stake, if an upgrade disrupts the functioning of bitcoin (eg, the attack vectors mentioned above), the majority of stakeholders would hesitate to add code quickly . ]

Nicolas Dorier, a Bitcoin Core collaborator, believes that it could still take a few years for Schnorr to be added to bitcoin.

And even Wuille, at the presentation, conceded that this delay might be necessary.

He concluded:

"I'd like to see what we're working on here merged with bitcoin, but it's a long process."

Disclosure: CoinDesk is a subsidiary of Digital Currency Group, which owns an interest in Blockstream.

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