What is Hash and Hashrate? Blockchain's Security Foundation

The birth of Bitcoin in 2009 not only marked a financial revolution but also introduced a sophisticated combination of applied cryptography and behavioral economics. In this structure, hash function and hash rate serve as irreplaceable pillars. According to experts at Tan Phat Digital, if you consider blockchain as an eternal data tower, the hash function is the cement that binds the bricks, while the hashrate is a huge source of energy that protects that tower against all attempts to sabotage.

1. The mathematical nature of cryptographic hash functions

A cryptographic hash function is an algorithm that transforms an input of any length into a fixed-length string of characters (hash value). To ensure Blockchain security, a hash function must meet the following strict properties:

• Pre-image resistance: The one-way nature makes it mathematically impossible to reverse the hash value to find the original data.

• Second pre-image resistance: Prevents finding a second message with the same hash value with a given message, ensuring data cannot be altered.

• Collision resistance: Highest level of security, requiring that finding any two messages with the same hash value is impossible in real time.

• Determinism: The same input data always produces a unique hash result, allowing Nodes in the network independently cross-check data.

• Avalanche effect: Even the smallest change in input (like changing 1 bit) will completely change the output hash value, causing any fraudulent behavior to be detected immediately.

2. Data structure and role of hash function

Blockchain uses hash function as a multi-layer data authentication mechanism, creating immutability for the entire chain:

• Block association: Each block contains the hash value of the previous block. If an attacker changes past data, the hash value of that block changes, breaking the entire connection of the blocks behind it.

• Merkle Tree: Transactions in the block are organized into a binary tree of hash values. The Merkle Root at the top of the tree represents the entire transaction and is included in the block header.

Verification Comparison: Full Node and Light Wallet

• Full Node:

  • Stores hundreds of GB (entire chain history).

  • Process: Checks every transaction and process Consensus rules.

  • Level: Completely self-verifying, no intermediaries needed.

• Light Wallet (SPV Client):

  • Stores several MB (80 bytes block header only).

  • Process: Only checks Merkle proof to confirm transaction is in block.

  • Level: Trust the chain with the highest difficulty.

3. Hashrate: The Driver of Cybersecurity

Hashrate is the total number of hash calculations that mining devices perform per second. As noted by Tan Phat Digital, Bitcoin's global hashrate has reached amazing records in the period 2025-2026.

Units of measuring computing power

• Megahash (MH/s): 1 million hashes/second.

• Gigahash (GH/s): 1 billion hashes/second.

• Terahash (TH/s): 1 trillion hashes/second.

• Petahash (PH/s): 1 quadrillion hashes/second.

• Exahash (EH/s): 1 trillion hashes/second.

• Zetahash (ZH/s): 1 trillion hashes/second. The Bitcoin network has officially exceeded the threshold of 1 Zetahash (1,000 EH/s) for the first time in history in 2025.

Economic barrier against 51% attacks

High hashrate creates an economic "firewall". By 2026, the cost to control 51% of the Bitcoin network power is estimated to be about 10 billion USD.1 This cost includes:

• About 4.6 billion USD for purchasing specialized hardware.

• 1.34 billion USD for building data center infrastructure.

• 130 million USD per week for electricity and transportation costs.

4. Consensus Mechanism and Difficulty Adjustment

Proof-of-Work (PoW) uses hashrate to solve the hash problem: $H(Block\_Header) \leq Target$. The difficulty adjustment algorithm (DAA) automatically changes the mathematical target every 2,016 blocks (about 2 weeks) to ensure the average block generation time is always 10 minutes.

However, the Bitcoin source code has a historical technical error called "off-by-one bug". Instead of measuring the time of the entire 2,016 blocks, the algorithm actually counts only the 2,015 intervals between blocks, skipping the first block of the cycle. However, this error has become part of the consensus rules to maintain network stability.

5. The Evolution of Mining Hardware

The hashrate race has pushed semiconductor technology to its physical limits:

• CPU Era (2009-2010): Mining using personal computers, extremely low performance.

• GPU Era (2010-2013): Using graphics cards for parallel computing However, performance increases dozens of times.

• ASIC Era (2013-Present): Specialized devices run only a single algorithm.

  • Antminer S19 XP (2022): Reaches 140 TH/s with a performance of 21.5 J/TH.

  • Antminer S21 XP Hydro (2025-2026): The pinnacle of technology with a capacity of 473 TH/s and impressive energy efficiency of 12 J/TH.

  • SealMiner A2 Pro Hydro (2026): A formidable competitor with hashrate up to 500 TH/s.

6. Case Study: Lessons from Security Practices

51% Attack on Bitcoin Gold (BTG)

Bitcoin Gold, a fork of Bitcoin that uses the Equihash algorithm to make it ASIC resistant, has fallen victim to severe 51% attacks. In May 2018, attackers controlled enough computing power to perform double-spending, appropriating approximately $18 million. Continuing in January 2020, the network was attacked again through two deep chain reorgs, causing tens of thousands of dollars in damage. This proves that networks with low hashrate and the ability to rent computing power (like through NiceHash) always pose a risk of manipulation.

The "great migration" of hashrate in 2021

In June 2021, China — the country that once accounted for more than 60%-75% of global hashrate — issued a comprehensive ban on cryptocurrency mining. This event caused the Bitcoin network hashrate to immediately drop by about 40%. However, instead of collapsing, miners moved equipment to more favorable legal areas such as Texas (USA), Kazakhstan and Russia. By the end of 2021, hashrate not only recovered but also set new records, confirming Bitcoin's self-balancing ability and strong decentralization.

7. Diverse hashing algorithms in the ecosystem

Each Blockchain chooses a hashing algorithm to optimize between security and decentralization:

• SHA-256 (Bitcoin): Gold standard for security, requires pure computing power and dedicated ASIC infrastructure.

• Scrypt (Litecoin, Dogecoin): Designed to "memory-hard", to resist ASIC dominance in the early stages. Currently the most powerful device is Antminer L9 with 16 GH/s.

• Ethash (Ethereum Classic): Optimized for GPU through large DAG data structure, helping to maintain decentralization in the community.

• X11 (Dash): Combines a chain of 11 different hash functions to enhance multi-layer security and save energy amount.

• Equihash (Zcash): Requires extremely high memory bandwidth, creating a major barrier to the production of efficient ASIC chips.

8. The future of cybersecurity: Stratum V2

With hashrate reaching the Zetahash threshold, the concentration of power in mining pools becomes a big risk. The Stratum V2 protocol is being deployed heavily in 2026 to solve this problem:

• Block control: Stratum V2 allows individual miners to choose transactions and build block headers themselves, instead of receiving blocks from mining pool operators. This prevents the risk of transaction censorship.

• Security: Uses AEAD encryption to prevent hashrate hijacking attacks that frequently occur on Stratum V1.

• Efficiency: Reduces data transmission bandwidth by 30%, good support for areas with limited internet connection.

Frequently Asked Questions (FAQ)

Question: Can the hash function be "decoded" to find the original data? Answer: Technically no. Cryptographic hash functions are designed to be "one-way functions". To find the original data, the only way is a brute-force attack — trying every possible input until the result matches. With modern algorithms like SHA-256, the number of calculations required is greater than the number of atoms in the observable universe.  

Question: Can quantum computers break the security of Blockchain? Answer: This risk remains more theoretical than real in 2026. Quantum computers threaten digital signature algorithms (like ECDSA) more than SHA-256 hash functions. SHA-256 is considered quite durable against quantum algorithms like Grover. However, about 25-30% of Bitcoin is currently located in addresses with exposed public keys, which could be at risk if quantum technology breaks through soon.

Question: Why does a high hashrate make the network more secure? Answer: A high hashrate means an attacker needs to own or rent a huge amount of machinery and electricity to overcome 51% of the network's power. Once the hashrate reaches Zetahash levels, plotting an attack becomes economically and logistically unfeasible because it is impossible to secretly acquire enough ASIC equipment.

In short, hash functions create the language of digital truth, and hashrate is the physical power that protects that truth. Through analysis from Tan Phat Digital, we see that this combination of mathematics and giant energy has created the most immutable, transparent and secure Blockchain network in human history.