Nakamoto Research

SHA-256

SHA-256 is very strong. It’s not like the incremental step from MD5 to SHA1. It can last several decades unless there’s some massive breakthrough attack.

If SHA-256 became completely broken, I think we could come to some agreement about what the honest block chain was before the trouble started, lock that in and continue from there with a new hash function.

If the hash breakdown came gradually, we could transition to a new hash in an orderly way. The software would be programmed to start using a new hash after a certain block number. Everyone would have to upgrade by that time. The software could save the new hash of all the old blocks to make sure a different block with the same old hash can’t be used.

— Satoshi Nakamoto, Bitcoin Talk, June 14, 2010

Bitcoin relies on the Secure Hash Algorithm 256 (SHA-256) hashing algorithm to ensure secure and transparent transactions. When a new block gets added to the chain, it contains a hash of the previous block’s hash, creating a permanent and unalterable record of all transactions that have occurred since the genesis block.

The SHA-256 algorithm takes input data of any size and produces a fixed-size 256-bit (32-byte) hash, making it virtually impossible to reverse or alter the data without significant computational power. This ensures that every transaction is time-stamped, publicly verifiable, and tamper-evident, maintaining the integrity and security of the Bitcoin network.

Bitcoin as a SHA-256 Rainbow Table?

There’s a speculative theory I’ve entertained myself at times that goes:

“What if Bitcoin is an experiment to develop capabilities for breaking the SHA-256 algorithm, and that the blockchain technically represents a collection of hashes akin to a set of Rainbow Tables?”

Unless some breakthrough is possible, it’s generally accepted that the SHA-256 hashes which comprise the Bitcoin blockchain aren’t enough information to create a usable Rainbow Tables style solution.

Bitcoin as a SHA-256 canary?

What if Bitcoin represents a canary that warns certain entities upon detection of a SHA-256 collision. Perhaps knowing ahead of time when something as critical as SHA-256 gets burned is worth the accidental creation of an entire one-trillion-dollar plus market cap finanaical system?

What about quantum computers?

The consensus is that SHA-256 is currently considered resistant to attacks by quantum computers in the near to medium term. Ongoing research efforts continue to assess its long-term security in a post-quantum world.

The primary quantum algorithm that poses a threat to cryptographic hash functions like SHA-256 is Grover’s algorithm. Grover’s algorithm provides a quadratic speedup for searching an unsorted database, useful in the application of finding hash collisions or preimages, but it requires a large, fault-tolerant quantum computer that doesn’t yet exist.

SHA-256 is secure against quantum attacks for the foreseeable future, but research in quantum computing and cryptography is rapidly evolving.

What about the new Microsoft Majorana 1?

Microsoft’s Majorana 1 quantum chip, unveiled on February 19, 2025, represents a significant step forward in quantum computing, leveraging a new state of matter called a topological superconductor to create more stable qubits.

In the context of Bitcoin, which relies on the SHA-256 hashing algorithm for its proof-of-work consensus and transaction integrity, this advancement raises questions about future security. SHA-256 is currently considered secure against classical computing attacks due to the immense computational power required to find collisions or reverse the hash, but quantum computing introduces a theoretical threat through algorithms like Grover’s algorithm.

Grover’s could, in principle, reduce the time needed to brute-force SHA-256 from an impractical scale to a quadratic speedup—meaning a problem that takes 2^256 steps classically might take roughly 2^128 steps with a quantum computer.

This kind of brute-force attack on SHA-256 still remains far beyond the capabilities of current technology, including Majorana 1.

Experts estimate that breaking SHA-256 effectively would require a quantum computer with millions to hundreds of millions of stable qubits—Microsoft’s current prototype is in the single-digit range, and their roadmap aims for a million qubits by 2027-2029.

Bitcoin’s mining ecosystem can also adapt. A quantum speedup could shift mining dynamics, but it wouldn’t necessarily break SHA-256 outright. More likely, it could enable faster hash collision searches, which isn’t an immediate fatal flaw for the network. The risk is theoretical for now, and Bitcoin developers have time to explore quantum-resistant alternatives like new hash functions.

  
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  │ ⚠ THIS CONTENT MAKES NO CLAIMS ABOUT THE IDENTITY OF SATOSHI NAKAMOTO │
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