Innovations & Trends

How Does a Hash Help Secure Blockchain Technology?

Blockchain technology has revolutionized many industries by providing a decentralized, secure, and transparent way to record transactions and data. One of the key components that enables blockchain security is cryptographic hashing. In this article, we will examine how hashes help secure blockchain technology.

What is a Cryptographic Hash?

A cryptographic hash function is a mathematical algorithm that takes an input of any size, like a digital file or blockchain block, and converts it into a fixed-size alphanumeric string output called a hash value or hash.

Some properties of cryptographic hashes:

  • One-way function – Easy to compute hashes for any input, but impossible to reverse the hashing process.
  • Deterministic – The same input always produces the same hash output.
  • Fast computation – Hashes can be quickly calculated, even for large inputs.
  • Avalanche effect – Small changes in input drastically change the hash output.

These attributes make hashes ideal for securing data like blockchain blocks.

How Blockchain Uses Hashes

There are a few key ways that hashing bolsters blockchain security:

1. Linking Blocks in the Chain

Each new block in a blockchain contains the hash value of the previous block. This effectively creates a chain where each new hash links to the previous one. If someone tampered with a previous block, it would change the block’s hash, which would break the chain.

2. Verifying Block Identity

A block’s unique hash value serves as a digital fingerprint to identify it and verify that the block contents are authentic. Even small changes to the block data would generate a completely different hash value.

3. Generating Block Addresses

Miners generate new blocks by solving computational puzzles known as proof-of-work. The puzzle involves finding a hash value below a target difficulty level set by the blockchain protocol. This process secures the network and verifies transactions.

4. Supporting Digital Signatures

Public and private keys used in digital signatures rely on hash functions. The private key generates a unique signature for each transaction that can be validated using the public key and message hash. This proves the transaction originated from the sender.

Key Properties that Secure Blockchains

Hashing functions have properties that make them exceptionally good for securing blockchains:

  • Irreversible – Unable to reverse hashes to reconstruct input data. Prevents tampering.
  • Collision resistant – Implausible to generate the same hash for different inputs. Unique fingerprint.
  • Puzzle friendliness – Enables proof-of-work and mining of new blocks.
  • Efficiency – Fast computation benefits the performance of transactions.

Common Hash Algorithms

While many hash functions exist, blockchain platforms typically use SHA-256 or Scrypt:

  • SHA-256 – Bitcoin and many others use this secure, 256-bit hash function.
  • Scrypt – Litecoin and some altcoins use this function that is more resistant to custom hardware attacks.

Hashing Enables Key Blockchain Attributes

By incorporating cryptographic hashing, blockchains gain several vital attributes:

  • Decentralization – No central party controls the network.
  • Transparency – Anyone can audit the public ledger of transactions.
  • Immutability – Modifying past blocks invalidates the blockchain.
  • Provenance – Traces origin and ownership history of assets.

This provides security while retaining an open, distributed architecture.

Common Questions about Hashes in Blockchains

How are hashes used in blockchain mining?

In proof-of-work mining, miners compete to find a valid hash under the target difficulty that solves the cryptographic puzzle and allows them to add the next block. This verifies work was done and transactions are valid.

What hash function does Bitcoin use?

The Bitcoin blockchain uses the SHA-256 cryptographic hash algorithm. It was designed by the NSA and offers high speed and reliability.

Can hackers reverse engineer hashes back to the original data?

No, cryptographic hash functions are deliberately one-way. It is virtually impossible to recover the original data from a hash value. This irreversibility secures the blockchain.

How fast are hashes produced?

Hash algorithms are designed to be extremely efficient. Even input files in gigabytes can be hashed quickly, making hashing practical for blockchain security and performance.


In summary, cryptographic hashing plays a critical role in blockchain security. Hashes enable linking blocks, providing digital fingerprints, facilitating mining, and supporting digital signatures. Key attributes like irreversibility, puzzle friendliness, and efficiency allow hashes to secure blockchains in a decentralized manner. By incorporating hashing functions, blockchains gain immutability, provenance tracking, and transparency.

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