With the continuous development of the Internet, more and more people understand some characteristics and usage of blockchain technology. Today, we will introduce some blockchain elements in Zhengzhou.

Blockchain Blockchain consists of blocks and chains.

Each block contains three elements: data, hash value and hash value of the previous block.

The first element of a block is data.

The data stored in the block is related to the type of blockchain.

For example, the blocks in the bitcoin blockchain store relevant transaction information, including sellers, buyers and the number of bitcoins traded.

The second element of the block is the hash value.

Each block contains a hash value. This hash value is yes. It is used to identify a block and all its contents.

Once a block is created, its hash value is calculated accordingly.

Changing something in the block will change the hash value.

So in other words: Hash values are very helpful when you want to detect changes in the content in a block.

If the fingerprint of a block changes, it is no longer the previous block.

The third element of the block is the hash value of the previous block.

This element makes it possible to form links between blocks and makes the blockchain very secure.

For example, suppose we have a blockchain with three blocks.

Each block contains its own hash value and the hash value of the previous block.

Block 3 points to block 2, which in turn points to block 1.

However, the 1 block is a bit special. It cannot point to the previous block because it is the first block.

We call 1 block genesis block.

Now let's assume that you tampered with the second piece.

This will cause the hash value of the second block to change, so the data stored in the third block is wrong and illegal.

Once the data stored in block 3 is illegal, the blocks behind it must also be illegal.

Therefore, if someone wants to tamper with any block in the blockchain, he must modify this block and all subsequent blocks.

This will be a very heavy task.

However, the workload of blockchain proves that the method of only using hash value is not enough to prevent users from tampering with blocks.

Because the current computer operation speed is powerful enough, and thousands of hash values can be calculated every second.

Java course/suggestion: You can tamper with one block and recalculate the hash values of other blocks, thus making your block legal again.