{"id":10960,"date":"2022-02-24T22:00:00","date_gmt":"2022-02-24T22:00:00","guid":{"rendered":"http:\/\/ci029aa92ae00024ff"},"modified":"2025-01-29T12:30:15","modified_gmt":"2025-01-29T12:30:15","slug":"how-mining-protects-the-bitcoin-network","status":"publish","type":"post","link":"https:\/\/bitcoinmagazine.com\/technical\/how-mining-protects-the-bitcoin-network","title":{"rendered":"How SHA256 And Mining Protect The Bitcoin Network"},"content":{"rendered":"
<\/div>

How mining works is fascinating. When I explain it to people, I enjoy seeing their face the moment their mind is blown. I\u2019ll explain it here, but just know, I\u2019m imagining all your faces as your minds blow!<\/p>\n

I have to start with hash functions. Without hash functions, Bitcoin would not be possible. Let me explain what they are first, not only so you can sound cool at parties, but also because it\u2019s fundamental to understanding how Bitcoin works \u2014 particularly mining but also transactions \u2014 under the hood. <\/p>\n

You don\u2019t need to understand how Bitcoin works in order to benefit from it, just like how you don\u2019t need to understand how TCP\/IP works to use the internet. But do go on, because it\u2019s quite interesting and I\u2019ll make it easy to understand, I promise. <\/p>\n

Hash Functions <\/h2>\n

Let\u2019s start with a schematic which I\u2019ll explain below\u2026 <\/p>\n

<\/figure>\n

On the left is the input, the center is the function, and on the right is the output. The input can be any data, as long as it\u2019s digital. It can be of any size, provided your computer can handle it. The data is passed to the SHA256 function. The function takes the data and calculates a random-looking number, but with special properties (discussed later).<\/p>\n

The first Secure Hash Algorithm (SHA) was originally developed by the NSA<\/a> and there are many different versions now (Bitcoin uses SHA256). It\u2019s a set of instructions for how to jumble up the data in a very complicated but specified way. The instructions are not a secret and it\u2019s even possible to do it by hand, but it is very tedious.<\/p>\n

For SHA256, the output is a 256-bit number (not a coincidence). <\/p>\n

A 256-bit number means a binary number 256 digits long. Binary means the value is represented with two symbols, either 0 or 1. Binary numbers can be converted to any other format, for example decimal numbers, which are what we are familiar with. <\/em><\/p>\n

Although the function returns a 256-digit binary number, the value is usually expressed in hexadecimal format, 64 digits long.<\/p>\n

Hexadecimal means that instead of 10 possible symbols like we are used to with decimal (0 to 9), we have 16 symbols (The ten we are used to, 0-9, plus the letters a, b, c, d, e, and f; which have the values 11 to 15). As an example, to represent the value of decimal 15 in hexadecimal, we just write \u201cf\u201d and it\u2019s the same value. There\u2019s plenty of information available online with a quick Google search if you need more elaboration. <\/em><\/p>\n

To demonstrate SHA256 in action, I can take the number 1 and run it through an online hash calculator<\/a>, and got this output (in hexadecimal): <\/p>\n

<\/figure>\n

The top box is the input, the bottom box is the resulting output.<\/p>\n

Note that all computers in the world will produce the same output, provided the input is the same and the SHA256 function is used.<\/p>\n

The hexadecimal number output, if converted to decimal, is (notice it takes more digits to write): <\/p>\n

48,635,463,943,209,834,798,109,814,161,294,753,926,839,975,257,569,795,305,637,098,542,720,658,922,315<\/p>\n

And converted to binary it is: <\/p>\n

11010111000011010110010011100111111111100110100111111001110000110011101011010111000000001001110111111110101101000111111010101110100011110101101101001001110101010100010001011110001110101001001110000000001111001010010110111011011011110000111010110110100101111010111001101011100110101110011010111001101011100110101110011010111001101011100111 <\/p>\n

Just out of interest, here is the same value in base 64<\/a>.<\/p>\n

1w1k5\/5p+cM61wCd\/rR+ro9bSdVEXjqTgDylu28OtpY= <\/p>\n

Note that the smallest possible value SHA256 could return is zero, but the LENGTH is still 256 bits. This is how zero is represented:<\/p>\n

0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000<\/p>\n

And the largest possible value is:<\/p>\n

1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111<\/p>\n

In decimal, that\u2019s:<\/p>\n

115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,935<\/p>\n

In hexadecimal, it is:<\/p>\n

FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF<\/p>\n

Note there are exactly 64 F\u2019s.<\/p>\n

Zero in hexadecimal can simply be written as one single zero, but for hash output, it\u2019s 64 of them to keep to the requirement of a fixed size output:<\/p>\n

0000000000000000000000000000000000000000000000000000000000000000<\/p>\n

Here is a summary of some facts about the hash function that are vital to appreciate:<\/p>\n