When discussing blockchain technology, terms like hash, hash value, and hashing algorithm frequently come up. Many people assume hashing is the security safeguard on the blockchain, but strictly speaking, it is not an encryption algorithm. Encryption implies the existence of decryption, whereas hashing is a one-way cryptographic function—an irreversible mapping from plaintext to ciphertext. It only involves an encryption process, with no decryption possible. Before diving into hashing algorithms, let's clarify what a hash is.
Understanding Hash / Hashing
Hashing, also referred to as "hashing," is a mathematical computer process that takes input information of any length and transforms it through a hashing algorithm into a fixed-length data fingerprint output. This output, typically a combination of letters and numbers, is known as the "hash value."
In essence, a hashing algorithm can be thought of as a message-digest algorithm that compresses messages or data into a smaller, fixed format. Due to its one-way operation, which possesses a certain degree of irreversibility, hashing has become a component of encryption algorithms. However, a complete encryption mechanism cannot rely solely on hashing.
To understand irreversibility simply, consider that 1+4=5 and 2+3=5. Even if you know the result is 5, you cannot determine the original input numbers.
Common Hashing Algorithms
Currently, common hashing algorithms include the international Message Digest (MD) series and Secure Hash Algorithm (SHA) series, as well as China's SM3 algorithm.
Among these, SHA-256 is one of the SHA series algorithms. Designed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST), it is named SHA-256 because its digest length is 256 bits. SHA-256 is one of the most secure methods for protecting digital information.
For example, calculating the SHA-256 hash value of the string "hello blockchain world, this is yeasy@github" yields: "db8305d71a9f2f90a3e118a9b49a4c381d2b80cf7bcef81930f30ab1832a3c90".
For a given file, if the SHA-256 hash computation results in the same value, it is highly probable that the file contents are identical, without needing to examine the original content.
What Is the Purpose of a Hashing Algorithm?
Although it may seem like an esoteric mathematical function, hashing algorithms are closely related to our daily lives.
For instance, in the early days of information transmission, insecure channels could lead to message corruption. How could the receiver efficiently verify message consistency? Repeatedly sending confirmations back and forth was highly inefficient. Hashing algorithms elegantly solve this problem. When Party A sends a message, they can perform a hash operation on the original text and append the resulting hash value for verification. Upon receiving the message, Party B can perform the same hash operation on the text and compare the hash values to verify the integrity of the transmitted and received information.
Hashing algorithms are also the most widely used algorithms in blockchain technology. They are extensively employed in constructing blocks and confirming transaction integrity. For example, in Bitcoin, hashing algorithms generate data digests from transactions. Each block contains the hash of the previous block, and the subsequent block contains the hash of the current block, forming an unbreakable, tamper-resistant chain.
Characteristics of Hashing Algorithms
Beyond enabling rapid content comparison, the concept of hashing is often applied in content-based addressing or naming algorithms. An excellent hashing algorithm should meet the following criteria:
Fast Forward Operation: Given the original text and the hashing algorithm, the hash value can be computed within limited time and resources.
Difficult to Reverse: Given a hash value, it is practically impossible to deduce the original input within a reasonable time frame, forming the basis of hash security.
Input Sensitivity: Any change in the original input information should result in a significantly different hash value.
Collision Avoidance: It should be exceedingly difficult to find two different plaintexts that produce the same hash value (i.e., avoid collisions).
As evident, hashing algorithms play a crucial role in network data and blockchain technology applications due to their ability to enable rapid verification and prevent data or transaction tampering during transmission. They are also key to understanding why blockchain technology possesses security and trustworthiness.
Frequently Asked Questions
What is a hashing algorithm used for?
Hashing algorithms are primarily used for data integrity verification, digital signatures, and ensuring information security in various applications, including blockchain and secure communication protocols.
Can hash values be decrypted?
No, hash values are designed to be irreversible. They are not encrypted data but rather unique fingerprints of the input, making decryption impossible.
Why is SHA-256 considered secure?
SHA-256 is considered secure due to its resistance to collision attacks, high input sensitivity, and the computational impracticality of reversing the hash or finding two inputs with the same output.
How does hashing protect blockchain transactions?
Hashing creates a tamper-evident chain by linking blocks through their hash values. Any alteration in a block would change its hash, breaking the chain and alerting the network to the inconsistency.
What is a hash collision?
A hash collision occurs when two different inputs produce the same hash output. While theoretically possible, secure algorithms like SHA-256 make collisions highly unlikely in practice.
Where can I learn more about implementing hashing?
👉 Explore practical hashing tutorials and tools for hands-on guidance and advanced techniques.