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---
layout: forum
title: 'Re: Dealing with SHA-256 Collisions'
grand_parent: Forum Posts
parent: Bitcoin Forum
nav_order: 115
date: 2010-06-14 20:39:50 UTC
original: https://bitcointalk.org/index.php?topic=191.msg1585#msg1585
---
# Re: Dealing with SHA-256 Collisions
---
```
Re: Dealing with SHA-256 Collisions
June 14, 2010, 08:39:50 PM
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.
```