<p>Facts [1]:</p>
<p>Hashing signature were build exactly to make this as much impossible as it could.
If someone manage to reverse the signatgure before next block validation, mean he found a new way/new algorithm to break hashing (even with quantum computer).
In such scenario were SHA-256 become vulnerable, Bitcoin wont be the only priotity as many other protocols such as internet and emails also use such hashing. A new signature algorithm'd made and quickly deployed everywere.</p>
<p>Facts [2]:</p>
<p>SHA is actualy quantum proof. The brut-force duration would be reduce by orders of magnetude using Grovers alorithms on qbits, tho we are still talking about billions of years, while Bitcoin block are mined usualy in 10 minutes.</p>
<p>You can find interesting discution about this on quora : <a href="https://www.quora.com/How-would-quantum-computers-render-one-way-hashing-algorithms-like-SHA-256-Bitcoin-useless-Would-they-somehow-be-able-to-reverse-the-hashes-or-would-they-just-be-better-at-finding-collisions" rel="nofollow noreferrer">https://www.quora.com/How-would-quantum-computers-render-one-way-hashing-algorithms-like-SHA-256-Bitcoin-useless-Would-they-somehow-be-able-to-reverse-the-hashes-or-would-they-just-be-better-at-finding-collisions</a></p>

CC BY-SA 4.0
2024-04-01T22:06:10.817Z
2024-04-01T22:06:10.817Z
Maxime CATY
<p>(I think this question will be blocked for being not specific, so help me edit it, thanks)</p>
<p>(I will present <strong>Facts [1]</strong> and <strong>Facts [2]</strong> which will help organize my ideas before my question)</p>
<p><strong>Facts [1]</strong>: (the following information is common sense)</p>
<p>One possible attack is: (reproducing the words in the blog <a href="https://braiins.com/blog/can-quantum-computers-51-attack-bitcoin" rel="nofollow noreferrer">braiins</a>)</p>
<blockquote>
<p>...public keys are <strong>revealed</strong> when transactions are broadcasted to the
mempool, even <strong>BEFORE</strong> they get added to the blockchain.</p>
<p>If an attacker could <strong>reverse the signature</strong> and get the associated
private key during this window before the transaction gets included
on-chain, they could then broadcast a higher-fee transaction sending
the coins to themselves instead.</p>
</blockquote>
<p><strong>Facts [2]</strong>: (the difficult part of the question will start here)</p>
<p>The paper <a href="https://ieeexplore.ieee.org/abstract/document/8697996" rel="nofollow noreferrer">A Survey on Various Attacks in Bitcoin and Cryptocurrency</a> describes 7 attacks:</p>
<pre><code>A. Denial-of-service Attack 
B. Double Spending Attack 
C. Sybil Attack 
D. Eclipse Attack 
E. Selfish mining Attack 
F. Fork after Withholding Attack 
G. Block Withholding Attack
</code></pre>
<p>I finally arrive to my question:</p>
<p><em>Using a quantum computer to break SHA-256/ECDSA:</em></p>
<p><strong>Are there other tricks to pull off a 51% attack throughout any of the (A-G) strategies?</strong></p>
<p>(I have tried to find any not widespreadly diffuse knowledge, like</p>
<p>For example 1: In Eclipse attack, the IP address of victim person is blocked or redirected towards a competitor. <a href="https://en.wikipedia.org/wiki/IPsec" rel="nofollow noreferrer">IPsec</a> uses SHA. So I think it is possible to find a vulnerability this way, but I have no idea how.</p>
<p>For example 2: It is written in the paper <a href="https://arxiv.org/pdf/2008.12981.pdf" rel="nofollow noreferrer">Off-Path TCP Exploits of the Mixed IPID Assignment</a>:</p>
<p><em>&quot;TCP connections DoS attack is particularly applicable to compromising applications secured by encrypted traffic, e.g., HTTPS and SSH&quot;</em>.</p>
<p>I have tried to guess which quantum attack to sha256 is able to attack bitcoin, but I am not a computer scientist so please ANY information is wellcome)</p>

<attack><majority-attack>
Can a 51% attack be triggered by any other of these 7 strategies? (and with a quantum computer?)
R. S.
# Can a 51% attack be triggered by any other of these 7 strategies? (and with a quantum computer?)

(Asked by: username_0 on 2024-03-26)

(I think this question will be blocked for being not specific, so help me edit it, thanks)

(I will present **Facts [1]** and **Facts [2]** which will help organize my ideas before my question)

**Facts [1]**: (the following information is common sense)

One possible attack is: (reproducing the words in the blog [braiins](https://braiins.com/blog/can-quantum-computers-51-attack-bitcoin))

> ...public keys are **revealed** when transactions are broadcasted to the
> mempool, even **BEFORE** they get added to the blockchain.
>
> If an attacker could **reverse the signature** and get the associated
> private key during this window before the transaction gets included
> on-chain, they could then broadcast a higher-fee transaction sending
> the coins to themselves instead.

**Facts [2]**: (the difficult part of the question will start here)

The paper [A Survey on Various Attacks in Bitcoin and Cryptocurrency](https://ieeexplore.ieee.org/abstract/document/8697996) describes 7 attacks:

```
A. Denial-of-service Attack 
B. Double Spending Attack 
C. Sybil Attack 
D. Eclipse Attack 
E. Selfish mining Attack 
F. Fork after Withholding Attack 
G. Block Withholding Attack

```

I finally arrive to my question:

*Using a quantum computer to break SHA-256/ECDSA:*

**Are there other tricks to pull off a 51% attack throughout any of the (A-G) strategies?**

(I have tried to find any not widespreadly diffuse knowledge, like

For example 1: In Eclipse attack, the IP address of victim person is blocked or redirected towards a competitor. [IPsec](https://en.wikipedia.org/wiki/IPsec) uses SHA. So I think it is possible to find a vulnerability this way, but I have no idea how.

For example 2: It is written in the paper [Off-Path TCP Exploits of the Mixed IPID Assignment](https://arxiv.org/pdf/2008.12981.pdf):

*"TCP connections DoS attack is particularly applicable to compromising applications secured by encrypted traffic, e.g., HTTPS and SSH"*.

I have tried to guess which quantum attack to sha256 is able to attack bitcoin, but I am not a computer scientist so please ANY information is wellcome)

**Tags:** attack, majority-attack


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## 1 answers

### Answer by username_1 on 2024-04-01. Score: 1

Facts [1]:

Hashing signature were build exactly to make this as much impossible as it could.
If someone manage to reverse the signatgure before next block validation, mean he found a new way/new algorithm to break hashing (even with quantum computer).
In such scenario were SHA-256 become vulnerable, Bitcoin wont be the only priotity as many other protocols such as internet and emails also use such hashing. A new signature algorithm'd made and quickly deployed everywere.

Facts [2]:

SHA is actualy quantum proof. The brut-force duration would be reduce by orders of magnetude using Grovers alorithms on qbits, tho we are still talking about billions of years, while Bitcoin block are mined usualy in 10 minutes.

You can find interesting discution about this on quora : <https://www.quora.com/How-would-quantum-computers-render-one-way-hashing-algorithms-like-SHA-256-Bitcoin-useless-Would-they-somehow-be-able-to-reverse-the-hashes-or-would-they-just-be-better-at-finding-collisions>


---

