<p>There was <a href="https://satoshi.nakamotoinstitute.org/posts/bitcointalk/threads/68/" rel="nofollow noreferrer">a similar question</a> to this on the BitcoinTalk forum in 2010, to which <a href="https://satoshi.nakamotoinstitute.org/posts/bitcointalk/threads/68/#6" rel="nofollow noreferrer">Satoshi Nakamoto contributed</a>:</p>
<blockquote>
<p>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.</p>
<p>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.</p>
<p>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.</p>
</blockquote>

CC BY-SA 4.0
2024-06-29T17:39:44.257Z
2024-06-29T17:39:44.257Z
Lee
<ol>
<li><p>If SHA256 is successfully attacked, what measures will be taken to replace the compromised hash function?</p>
</li>
<li><p>In the event of a SHA256 attack, will it be necessary to re-timestamp the entire blockchain from the beginning?</p>
</li>
<li><p>What are the potential challenges and implications of switching to a new hash function in the blockchain?</p>
</li>
</ol>

CC BY-SA 4.0
2024-06-29T14:53:06.690Z
This question is similar to: [If SHA256 and/or RIPEMD-160 were broken, would all bitcoin addresses be compromised?](https://bitcoin.stackexchange.com/questions/8702/if-sha256-and-or-ripemd-160-were-broken-would-all-bitcoin-addresses-be-compromi). If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem.
RedGrittyBrick
<blockchain><hash><attack><sha256>
If SHA256 is successfully attacked, will we need to replace the hash function and re-timestamp the entire blockchain from the beginning?
BitcoinFanatic
# If SHA256 is successfully attacked, will we need to replace the hash function and re-timestamp the entire blockchain from the beginning?

(Asked by: username_0 on 2024-06-29)

1. If SHA256 is successfully attacked, what measures will be taken to replace the compromised hash function?
2. In the event of a SHA256 attack, will it be necessary to re-timestamp the entire blockchain from the beginning?
3. What are the potential challenges and implications of switching to a new hash function in the blockchain?

**Tags:** blockchain, hash, attack, sha256

> **Comments:**
> **username_1**: This question is similar to: [If SHA256 and/or RIPEMD-160 were broken, would all bitcoin addresses be compromised?](https://bitcoin.stackexchange.com/questions/8702/if-sha256-and-or-ripemd-160-were-broken-would-all-bitcoin-addresses-be-compromi). If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem.  

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## 1 answers

### Answer by username_2 on 2024-06-29. Score: 1 | Accepted answer

There was [a similar question](https://satoshi.nakamotoinstitute.org/posts/bitcointalk/threads/68/) to this on the BitcoinTalk forum in 2010, to which [Satoshi Nakamoto contributed](https://satoshi.nakamotoinstitute.org/posts/bitcointalk/threads/68/#6):

> 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.


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