Chapter 0 Introduction

Congratulations to Liu Cixin for winning the Hugo Award for Best Novel for his novel The Three-Body Problem. As a fan, I must write something to express my gratitude for the work.

As a fictional literary work, especially a novel, it is enough for me to read it once. When I think of the story in the future, my brain waves will fluctuate a little, and I have almost no desire to pick up the book and read it again. But "The Three-Body Problem" is an exception. It makes me excited when I think of it, and I can't wait to read it again. The "Three-Body Problem" trilogy is hard science fiction. The technical descriptions and logical thinking in it are very meticulous and advanced. This will scare some liberal arts students, but this is the core charm of science fiction works. Crazy and unreal imagination, transcendental thinking, behind which solid details and strong logic are needed.

This article will talk about two descriptions of a technology in "The Three-Body Problem". This technology is so close to the principles of Bitcoin that we love.

Chapter 1: The "Cradle" of Wallfacer Rey Diaz

The way Rey Diaz fights against the invasion of the Trisolarians is this: place one million stellar-level hydrogen bombs on Mercury. If the Trisolarian civilization is about to invade the Earth, then he will issue a declaration to the Trisolarian world that "humanity will perish with them" to the omnipresent Sophons, detonate nuclear bombs and blow up the entire solar system, thus threatening the Trisolarian civilization.

As part of the Wallfacer Plan, once the Trisolarian civilization knew this information, they could kill the person who could detonate the nuclear bomb, Rey Diaz, to prevent the detonation. In order to avoid being killed, Rey Diaz designed the detonation method of the nuclear bomb into a "cradle".

"Cradle" means that if the cradle stops rocking, the baby will wake up. Diaz uses a watch-like device to continuously send signals to Mercury, and the hydrogen bomb system on Mercury continuously receives the signals. Once the signal is interrupted, the system will immediately detonate the hydrogen bomb. This is called the "anti-trigger system."

The "cradle" signal source collects Diaz's heartbeat, blood pressure, body temperature, etc., and conducts a comprehensive analysis of these parameters. If any abnormality is found, the anti-trigger signal emission will be stopped immediately, and the hydrogen bomb will be detonated.

But the anti-trigger system can be cracked. The signal is transmitted from Rediaz on Earth to Mercury over a complex communication link (look, Bitcoin enthusiasts, the "chain" has appeared). Destroying or shielding any node on the link, and then using a fake signal source to continue sending the anti-trigger signal to the next level link, can render the "Cradle" system ineffective.

But here comes the problem. All signal nodes can be encrypted. All nodes use the same encryption algorithm. Each signal sent is generated by this algorithm. To the outside world, each signal is random and different each time. However, the sender and receiver of the "cradle" produce exactly the same or regular sequence values ​​(programmers, have you seen the soul of the "hash function"?). The receiver considers the signal valid only when it receives a signal value corresponding to its own sequence. If the encryption algorithm is not cracked, the pseudo signal is invalid.

Cracking an encryption algorithm is not difficult in human civilization, let alone the Three-Body World, a civilization that can operate the technology of the 11-dimensional world, use dimensionality reduction to expand particles and etch them into integrated circuits to make supercomputers. Cracking this encryption algorithm will definitely be a matter of minutes.

So what can we do? How can we design an encryption system that is immune to being cracked?

Climax warning, the climax is coming, please be prepared to be surprised.

I will first quote the original text

"It's a stupid way. I can only think of crude and stupid ways." Rey Diaz laughed at himself and said, "Increase the sensitivity of each node to its own status monitoring. The specific method is that each communication node is composed of multiple units. These units are far apart, but they are connected to each other by continuous communication. If any unit fails, the entire node will issue a command to terminate the anti-trigger. After that, even if the pseudo-signal source sends a signal to the next node, it will not be recognized. The monitoring accuracy between the units can currently reach the microsecond level. That is to say, according to the method of the gentleman just now, all the units that make up a node must be destroyed at the same time within one microsecond, and then the pseudo-signal source is used for signal connection. Each node is composed of at least three units, and there may be dozens of units at most. The distance between these units is about 300 kilometers, and each one is made extremely solid. Any external trigger will cause it to send a warning. It may be possible for the Trisolarans to make these units fail at the same time within one microsecond, but humans certainly cannot do it at present." (Excerpt from "The Three-Body Problem II: Dark Forest" Crisis Chronicle Year 20, the Trisolaran fleet is 4.15 light years away from the solar system)

Let me draw a picture.

Each "unit" in the diagram can detect the information of the previous unit. If any "unit" in the middle is replaced or has some additional information added, it will be rejected by the following units.

If you want to forge this communication node composed of communication units, you must completely encrypt the communication units that have been sent in the entire communication node and use the same encryption algorithm to generate the same next communication unit. All this work must be done in microseconds and faster than the original signal transmission system.

If the communication nodes use the same inter-unit contact monitoring method, the communication chain between the Earth and Mercury will be indestructible.

In fact, this is the core concept of Bitcoin.

Chapter 2: The "Cradle" of Wallfacer Luo Ji

The second time a communication link appears in The Three-Body Problem is at the end of The Dark Forest.

Luo Ji deployed 3,614 nuclear bombs in the solar orbit. After the nuclear bombs were detonated, the sunlight and interstellar dust caused by the nuclear explosion would broadcast the coordinates of the Centaurus Galaxy and the solar system in the universe to the universe, thereby triggering the dark forest attack of other civilizations on the two civilizations of the Three-Body World and human beings.

The system that triggered the explosion of more than 3,000 nuclear bombs was a signal link. The original description is as follows:

"This is a vital signs monitor, which is connected to a cradle system through a transmitter. You must remember what happened to Wallwright Rey Diaz two centuries ago, and you must know what the cradle system is. The signal sent by this monitor passes through the link of the cradle system and reaches the 3,614 nuclear bombs deployed by the Snow Project in the solar orbit. The signal is emitted once a second to maintain the non-triggered state of these nuclear bombs. If I die, the maintenance signal of the cradle system will disappear,..."

The original text did not provide any further description of this link system, except for a sentence added later by Luo Ji:

"No, this device is much more advanced than Rey Diaz's. As long as I'm alive, the signal will not be interrupted."

Chapter 3 Bitcoin Blockchain

To fully understand Bitcoin, you need to understand at least the following concepts: 1. Public and private key digital signatures; 2. Blockchain; 3. Timestamps; 4. Proof of Work. I will briefly describe the blockchain here to compare it with the "cradle" system in "The Three-Body Problem".

A "block" is a data packet. We can imagine it as a packaged package containing a notebook that records data. These data can be imagined as an accounting book.

"Blockchain" refers to a chain formed by blocks connected end to end.

The picture below can be seen as two blocks of the blockchain that carries Bitcoin.

The picture below can be seen as a model of the block.

Now let me explain blockchain in a simpler way.

Accountants use double-entry books to keep accounts for individuals, companies or other organizations, recording page by page to form a complete book. But if someone tears a page from the middle, or burns a book from a pile of books, it can be done without leaving any trace. This is why bookkeeping needs to be done by a group of trustworthy people, and accountants must have professional ethics.

If you use a computer to keep accounts, a "page header" will be recorded at the beginning of each page of the account book, which contains the information of all previous pages, including the order between pages. That is, the information of all previous pages is converted into a recordable data through an encryption algorithm. If there is any modification to the previous page, the same encryption algorithm will produce a different result.

When recording a page, this page will be placed at the end of the chain. Each page of the account book will extend the chain by one section and put itself at the end.

The "page" here is the block.

The "page header" here refers to the block header information.

The "encryption algorithm" here is the hash function.

The "page chain" here is the blockchain.

If you want to forge a blockchain formed in this way, you must copy all the existing chains that have already been formed, and use computing power faster than the current accounting computers to generate the next block.

And now (as of August 29, 2015), the blockchain that carries the Bitcoin system has a total of 372,016 blocks, with a total data capacity of 40G, and the computing power of the computer that accounts for this Bitcoin system has reached 400P, that is, 400 quadrillion floating-point calculations. The computing power of my country's Tianhe-2 supercomputer is 33P.

The Bitcoin blockchain is indestructible.

Chapter 4 Blockchain and the “Cradle”

The core concept of blockchain is that blocks are connected one by one to form a chain. Each newly added block is linked to the end of the chain, and each block must contain the encrypted signal of the entire previous chain.

The core concept of the "cradle" is that communication units are connected one by one to form a chain. Each newly added communication unit is linked to the end of the chain, and each communication unit must contain information to monitor the previous chain.

There are so many similarities between these two concepts. Liu Cixin published The Three-Body Problem II: The Dark Forest in May 2008, in which he wrote about the Cradle System in a sci-fi style. Satoshi Nakamoto first proposed Bitcoin in a paper titled Bitcoin: A Peer-to-Peer Electronic Cash System published in 2008.

Liu Cixin is a genius. Satoshi Nakamoto is a genius.

Chapter 5 Conclusion

"The Three-Body Problem" is so well written that life without reading it would be an incomplete life.

Bitcoin is so well designed that a life without Bitcoin is an incomplete life.