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When the technology called "blockchain" is discussed, it is often spoken of in terms of dream-like expectations. What is the reality of the situation?

Blockchain is a ledger technology created to realize the digital currency Bitcoin. It aims to (1) store and maintain the content and existence of records so that no one can deny them, (2) allow anyone to verify their validity, and (3) prevent anyone from stopping the entry of valid records.

In other words, it aims to ensure that "the end-user (as an endpoint), rather than a central authority, has full power over (the records of) assets." It can be said to embody the philosophy of internet decentralization in the control of assets. While some describe blockchain as an "invention second only to the internet," in this sense, it would be more accurate to say that blockchain is something "intended to complement the internet."

Now, technically, we need to distinguish between the "denial of content" and the "denial of existence" of a record. Denial of content can be made impossible through digital signatures. If a record has a digital signature, any tampering will be detectable. However, existence is not so simple. Since deleting the record itself constitutes a denial of existence, digital signatures alone cannot solve this.

Therefore, blockchain essentially "publishes the record in a newspaper." It establishes it as a well-known fact. Of course, if it were published in an actual newspaper, it would be inevitable that a situation could arise where it is "stopped by someone," such as the newspaper company refusing to publish the article or the newspaper itself going out of business. Thus, through the autonomous and decentralized actions of participants, an image is shared as if everyone were looking at the same newspaper. What is used at this time is "Proof of Work."

Proof of Work generally indicates that one cannot proceed to the next process without leaving evidence that the assigned work was actually performed. The idea is to deter fraud by setting a hurdle of paying a cost before using a service. When applied to the storage and maintenance of records, it means that records will not be saved unless the assigned work is performed. At the same time, since the records cannot be overturned without performing the same amount of work, it becomes resistant to tampering.

Since this work is performed by miners, some describe it as "mining" or "solving a puzzle," but since it is actually a pure matter of probability, it should more accurately be called a "lottery." Because it is a lottery, intelligence is not required. While blockchain is sometimes said to be "impossible to tamper with," anyone can tamper with it regardless of ability if they can complete a vast number of lottery draws in a short period—that is, if they are willing to pay a massive cost.

Including such issues, current blockchain technology faces many technical challenges. Because it operates probabilistically, it does not necessarily move at the same tempo as our lives in real-time. Furthermore, since all participating miners basically perform the same processing, the load is not distributed, making it unable to withstand scaling. Attempting to adopt new technology causes the recorded history to fork, making it impossible to test in the field, which in turn makes it vulnerable to technological obsolescence. Moreover, the reason miners maintain the system's resistance to tampering by paying the enormous cost of the lottery is that they receive rewards in currency like Bitcoin; if the currency crashes and the cost of the lottery can no longer be paid, miners will be forced to withdraw. Consequently, the strength against tampering will be lost.

There are many attempts to address these challenges using technology to create private ledgers. This is because the challenges become simpler in a network consisting of specific participants. However, that would be like publishing records in an "internal newsletter" compared to a "newspaper," resulting in lower evidentiary value. Doubts would persist that someone within the company might change the records later.

Returning to the title of this article, the focus of this technology is rather the question of "how we can carve an unchangeable history." As social infrastructure becomes automated in various aspects, the significance of being able to maintain records that cannot be overturned even by AI is substantial.

The authors recently released a technology named "BBc-1 (Beyond Blockchain One)." This is designed so that even when leaving records in an "internal newsletter," the newsletters can have sufficiently high evidentiary value by linking with each other while keeping their contents secret. Beyond this, I expect many other challenges will be undertaken in the future, that what is said to be possible with blockchain will actually become possible, and that the automation of society's trust infrastructure will proceed in earnest.

*Affiliations and titles are as of the time of publication.