<p>Becuase transaction T2 has different contents (address adversary owns rather than address vendor owns) it will have a different hash.</p>

CC BY-SA 3.0
2018-03-31T09:21:37.033Z
Sorry, I haven't written in my question, but I meant that T2 has same hash because adversary found second pre-image of hash function.
Some One
CC BY-SA 3.0
2018-03-31T11:12:05.627Z
Okay, the adversary has super-human reverse hashing power? Some kind of superhero?
Willtech
CC BY-SA 3.0
2018-03-30T21:01:52.987Z
2018-03-30T21:01:52.987Z
Willtech
<p>Let's consider following situation:</p>

<ol>
<li>Vendor owns address <em>X</em>.</li>
<li>Adversary sends transaction <em>T1</em> to <em>X</em> with hash <em>Y</em> and receives product from vendor.</li>
<li>Adversary sends transaction <em>T2</em> to address which he owns with the same hash Y to other nodes.</li>
<li>Vendor receives transaction <em>T2</em> with same hash as <em>T1</em>, so from his point of view this is the same transaction. He ignores it.</li>
<li>Other nodes receives transaction <em>T1</em> after <em>T2</em> so they ignores <em>T1</em>.</li>
<li>Transaction <em>T2</em> was sent to majority, so probability that <em>T2</em> will be included in next block is higher than probability of inlcuding <em>T1</em>.</li>
<li>According to probabilty, the transaction <em>T2</em> was included in next block.</li>
</ol>

<p>Is this scenario of double-spend correct?</p>

<transactions><hash><doublespend>
How two transactions with the same hash can cause double-spending
Some One
# How two transactions with the same hash can cause double-spending

(Asked by: username_0 on 2018-03-30)

Let's consider following situation:

1. Vendor owns address *X*.
2. Adversary sends transaction *T1* to *X* with hash *Y* and receives product from vendor.
3. Adversary sends transaction *T2* to address which he owns with the same hash Y to other nodes.
4. Vendor receives transaction *T2* with same hash as *T1*, so from his point of view this is the same transaction. He ignores it.
5. Other nodes receives transaction *T1* after *T2* so they ignores *T1*.
6. Transaction *T2* was sent to majority, so probability that *T2* will be included in next block is higher than probability of inlcuding *T1*.
7. According to probabilty, the transaction *T2* was included in next block.

Is this scenario of double-spend correct?

**Tags:** transactions, hash, doublespend


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## 1 answers

### Answer by username_1 on 2018-03-30. Score: 0

Becuase transaction T2 has different contents (address adversary owns rather than address vendor owns) it will have a different hash.

> **Comments:**
> **username_0**: Sorry, I haven't written in my question, but I meant that T2 has same hash because adversary found second pre-image of hash function.  
> **username_1**: Okay, the adversary has super-human reverse hashing power? Some kind of superhero?  

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