OKX Blockchain 60 Lessons | Episode 11: Cryptography in Blockchain (Part 1)
"OKX Blockchain 60 Lessons" is a blockchain educational animated video series jointly produced by OKX and Sina Technology. It targets users with zero baseline knowledge of blockchain and uses articles, animated videos, and other formats to vividly explain blockchain concepts through 5 major sections and 60 knowledge points, covering concepts, technology, and applications. The content of this episode was guided by Xiong Yue, Partner at Bitxin.
Hello everyone, I'm Xiao K. Today we're going to cover: "Cryptography in Blockchain (Part 1)."
As we discussed before, the four core technologies of blockchain are cryptography, distributed ledger, consensus mechanism, and smart contracts. Cryptography is the most important among them, as it protects the security of the blockchain system — you could say it is the cornerstone of blockchain. All other technologies are built upon this foundation, allowing us to construct the towering edifice of blockchain.
Blockchain primarily uses two branches of cryptography: one is hash algorithms, and the other is asymmetric encryption. In this lesson, Xiao K. will mainly explain what "hash algorithms" are in blockchain cryptography.
Simply put, a hash algorithm is a special kind of function — no matter how long a string of characters you input, the function always produces an output of a fixed length. Think of it like an ID card number: whether you're from Beijing or Shanghai, everyone's ID card number is 18 digits and unique nationwide.
Similarly, hashing is also a compression mapping — it can transform input of any length into output of a fixed length, always a fixed 256 bits. This resulting output value is called the hash value.
Hash algorithms have three characteristics: one-wayness, tamper resistance, and collision resistance. These give blockchain its immutability, anonymity, and other features, and protect the security of the entire blockchain system.
Let's start with the first characteristic: one-wayness. One-wayness means that in a hash function, you can derive output from input, but it is virtually impossible to reverse-engineer the input from the output. For example, if we input a known string A and get the hash value F(A), we cannot work backward from this hash value F(A) to recover the data we input.
When blockchain packages data into blocks, the data is all processed through hash algorithms. It is precisely based on the one-wayness of hash algorithms that blockchain effectively protects the security of our information.
The second characteristic of hash algorithms is tamper resistance. Tamper resistance means that for any input, even a very small change — such as a single punctuation mark — will cause the hash value to change dramatically.
This feature plays a critical role in the linking between blocks.
Each block in the blockchain uses the hash value of the previous block as its identifier, which is then processed through the hash algorithm. This way, subsequent blocks can not only look up all preceding blocks but also verify whether the data in preceding blocks has been altered. Unless someone can crack all the hash values across the entire chain, once data is recorded on the chain, it is impossible to tamper with.
The third characteristic of hash algorithms is collision resistance. Collision refers to when two different input data values produce the same output — similar to running into someone wearing the same outfit while shopping.
Collision resistance means that for most inputs, a unique output can be obtained. Note that we can only say the probability of a collision is extremely low, but it does not mean collisions are impossible, because none of the existing hash algorithms can be proven mathematically to never experience collisions.
The third characteristic of hash algorithms is primarily applied in blockchain account addresses. In the world of blockchain, every transaction and account address is generated entirely based on hash algorithms. The purpose of this is to ensure the uniqueness of transaction or account addresses within the blockchain network — no matter how much money I transfer or how many people I send it to, it remains a unique entry in blockchain's grand ledger.
Overall, hash algorithms are the most fundamental element in blockchain technology. They are like the white blood cells in our bodies — not only is every part of blockchain dependent on them, but they also endow blockchain with its various features, protecting the security of the entire blockchain system.
Thanks to Teacher Xiong Yue for his assistance and guidance on the content of this episode.
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