<blockquote>
<p><strong>where these unconfirmed transactions are stored before being included in block</strong></p>
</blockquote>
<p><strong>Mempool</strong></p>
<p>Each node (wallet, miner, etc) stores them in a local collection called the &quot;mempool&quot;. The name implies these are typically kept in memory (RAM) but the developers of each wallet software can decide whether to also store the data onto non-volatile storage such as disk.</p>
<blockquote>
<p><strong>Can they be modified before a [miner] put them in blockchain</strong></p>
</blockquote>
<p><strong>No, because they are each signed</strong></p>
<p>Modifying the transaction would make the transaction <a href="https://en.wikipedia.org/wiki/Digital_signature" rel="nofollow noreferrer">signature</a> fail verification.  Only the person who knows the secret number known as a private key can produce a valid signature for a transaction. The inputs to a transaction are locked by a script that can only be satisfied by a number resulting from the use of the private key.</p>
<p>Every other node (wallet, miner etc) would reject a modified transaction and start to suspect the source as being potentially malicious.</p>

CC BY-SA 4.0
2021-03-13T12:08:23.150Z
2021-03-13T12:14:34.483Z
2021-03-13T12:14:34.483Z
RedGrittyBrick
<p>I am beginner and I am still learning fundamentals of block and bitcoin network.</p>
<p>Suppose, I do a transaction on bitcoin network, it is marked as unconfirmed transaction and is stored in <em><strong>mempool</strong></em> of full nodes.</p>
<p>This unconfirmed distributed over network, at some point a minor will create a block which will contain this transaction.</p>
<p>My question is where these unconfirmed transactions are stored before being included in block or hence block chain?</p>
<p>Can they be modified before a minor put them in blockchain?</p>

<bitcoin-core><blockchain><unconfirmed-transactions>
Can a unconfirmed transaction be lost or modified?
sujeet
# Can a unconfirmed transaction be lost or modified?

(Asked by: username_0 on 2021-03-13)

I am beginner and I am still learning fundamentals of block and bitcoin network.

Suppose, I do a transaction on bitcoin network, it is marked as unconfirmed transaction and is stored in ***mempool*** of full nodes.

This unconfirmed distributed over network, at some point a minor will create a block which will contain this transaction.

My question is where these unconfirmed transactions are stored before being included in block or hence block chain?

Can they be modified before a minor put them in blockchain?

**Tags:** bitcoin-core, blockchain, unconfirmed-transactions


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## 1 answers

### Answer by username_1 on 2021-03-13. Score: 1 | Accepted answer

> **where these unconfirmed transactions are stored before being included in block**

**Mempool**

Each node (wallet, miner, etc) stores them in a local collection called the "mempool". The name implies these are typically kept in memory (RAM) but the developers of each wallet software can decide whether to also store the data onto non-volatile storage such as disk.

> **Can they be modified before a [miner] put them in blockchain**

**No, because they are each signed**

Modifying the transaction would make the transaction [signature](https://en.wikipedia.org/wiki/Digital_signature) fail verification. Only the person who knows the secret number known as a private key can produce a valid signature for a transaction. The inputs to a transaction are locked by a script that can only be satisfied by a number resulting from the use of the private key.

Every other node (wallet, miner etc) would reject a modified transaction and start to suspect the source as being potentially malicious.


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