For friends who have been exposed to or purchased digital collections, there is a "hash value" on each digital collection, these so-called "hash values" consist of a long string of numbers + letters, and the characters of each collection are automatically generated and completed differently.
What exactly does this character, called hash, mean? We can learn through online retrieval of information, but more authoritative explanation, I think or the letter published in 2018 "Blockchain - the fact machine that empowers all things" in the book, the concept of hash value has been interpreted and elaborated in detail, interested friends, let's learn together.
Digital collections, also known as NFTs (non-homogeneous tokens), in fact, the digital collections that we now contact or buy and play with originated from blockchain technology, and more directly, from Bitcoin under blockchain technology. Therefore, to understand this hash value in detail, it is also necessary to start from Bitcoin, it can be said that the design of the digital collection is based on the technology of Bitcoin.
As we all know, Bitcoin originated from "mining". In fact, during each block cycle of mining, miners who try to get the next Bitcoin reward will participate in the proof-of-work competition, and they will simultaneously collect the newly generated transactions and put them in their respective new blocks. For the details of each transaction of the mined bitcoin, such as the date, time, sender and recipient address, sending amount, etc., will be collected and generated by a special cryptographic algorithm to generate a string of letters and numbers, this string is the hash value (hash).
According to the introduction, a hashing algorithm can convert raw data of any length into a unique fixed-length string of letters and numbers, which can mathematically prove the existence of its underlying information. Anyone with transaction information can easily enter it into the same hashing algorithm to confirm that the person who originally generated the hash must have the same data. Another key feature of a hash value is that it is sensitive to changes in its underlying data.
The following is the hash value we obtained by entering the text of the previous paragraph into the highly reliable SHA-256 algorithm (the hashing algorithm used by Bitcoin): 63f48074e26b1dcd6ec26be74b35e49bd31a36f849033bdee4194b6be8505fd9. Now, notice that when we simply remove the period of that text, the same algorithm produces a very different string of letters and numbers: 8f5967a42c6dc39757c2e6be4368c6c5f066647cc3c73d3aa2c0abdec3c6007a5.
You can think about how important such a high sensitivity as hashing algorithms is to maintaining the integrity of the blockchain. If someone tries to introduce a modification into an existing transaction, other miners will obviously find that the newly generated hash does not match the corresponding record on their respective version of the blockchain and will reject the modification.
It can be said that this information on the blockchain can only be added according to the contract, but it cannot be tampered with, and because of this, whether it is a digital collection, or Bitcoin, Ether, it has this feature, and the process of circulation will be recorded in detail, but it can never be tampered with.