<p>A bitcoin private key is 256 bits. So you would need about 24 words (bip39 draws from 2048 words) to equal that. (2048^24= about 3x10^79
2^256= about 1x10^77)</p>

CC BY-SA 4.0
2019-03-17T21:53:24.977Z
2019-03-17T21:53:24.977Z
Newb on Linux Fedora
<p>Notice in the actual unsafe working examples below that:</p>

<ol>
<li><p>12 words utilizes 128 (4x32) bits of entropy</p></li>
<li><p>18 words utilizes 192 (4x48) bits of entropy</p></li>
<li><p>24 words utilized 256 (4x64) bits of entropy</p></li>
</ol>

<p>Note the results below can be easily extended to 15 and 21 BIP 39 seed words.</p>

<p><code>% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-32 | bx mnemonic-new</code></p>

<p><strong>health boil host ostrich fire spike body solar collect harvest catalog crystal</strong></p>

<p><code>% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-48 | bx mnemonic-new</code></p>

<p><strong>health boil host ostrich fire spike body solar collect harvest catalog cup mix tattoo market festival sudden please</strong></p>

<p><code>% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-64 | bx mnemonic-new</code></p>

<p><strong>health boil host ostrich fire spike body solar collect harvest catalog cup mix tattoo market festival sudden pony notable beach wide health original inform</strong></p>

<p>Also note the repetition of the BIP 39 words above.</p>

CC BY-SA 4.0
2019-03-18T03:11:49.840Z
2019-03-18T03:11:49.840Z
skaht
<p>Well for starters that should exponentially increase the security of the password if anything else</p>

CC BY-SA 3.0
2018-03-06T12:37:10.873Z
2018-03-06T12:37:10.873Z
a1nb0
<p>The English-language wordlist for the BIP39 standard has 2048 words, so if the phrase contained only 12 random words, the number of possible combinations would be 2048^12 = 2^132, and the phrase would have 132 bits of security. However, some of the data in a BIP39 phrase is not random, so the actual security of a 12-word BIP39 mnemonic phrase is only 128 bits. This is approximately the same strength as all Bitcoin private keys, so most experts consider it to be sufficiently secure.</p>

CC BY-SA 4.0
2019-01-22T15:59:21.480Z
How does this answer the question of why some wallets use 24 word mnemonic?
Sergei Tikhomirov
CC BY-SA 4.0
2019-01-22T19:34:28.393Z
24-word is much secure but 12-word is enough
Tailer
CC BY-SA 4.0
2019-01-23T16:03:51.060Z
Do developers of the wallets which use 24 words not understand this? Why don't they go for 48 words to be even _more_ secure?..
Sergei Tikhomirov
CC BY-SA 4.0
2019-01-27T00:44:36.387Z
@SergeiTikhomirov 12-word seed is really enough and secure
Tailer
CC BY-SA 4.0
2021-03-09T20:01:31.640Z
In Bitcoin, a private key is a 256-bit number ...
Laurent Debricon
CC BY-SA 4.0
2022-11-14T18:05:03.427Z
It sounds like the real answer is risk/reward as perceived by the manufactures. Some feel the risk of using 12 words is worth the reward of more customers because they feel that 1) 12 is secure enough and 2) they can get more customers because they would rather deal with half the words.
Love to Code
CC BY-SA 3.0
2018-03-06T12:41:10.380Z
2018-03-06T12:41:10.380Z
Tailer
<p>Why was the format switched to 24 words for some newer wallets?</p>

<seed>
What's the difference between 12 word seed and 24 word seed?
ripper234
# What's the difference between 12 word seed and 24 word seed?

(Asked by: username_0 on 2018-03-06)

Why was the format switched to 24 words for some newer wallets?

**Tags:** seed


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## 4 answers

### Answer by username_4 on 2018-03-06. Score: 6 | Accepted answer

The English-language wordlist for the BIP39 standard has 2048 words, so if the phrase contained only 12 random words, the number of possible combinations would be 2048^12 = 2^132, and the phrase would have 132 bits of security. However, some of the data in a BIP39 phrase is not random, so the actual security of a 12-word BIP39 mnemonic phrase is only 128 bits. This is approximately the same strength as all Bitcoin private keys, so most experts consider it to be sufficiently secure.

> **Comments:**
> **username_5**: How does this answer the question of why some wallets use 24 word mnemonic?  
> **username_4**: 24-word is much secure but 12-word is enough  
> **username_5**: Do developers of the wallets which use 24 words not understand this? Why don't they go for 48 words to be even _more_ secure?..  
> **username_4**: @username_5 12-word seed is really enough and secure  
> **username_6**: In Bitcoin, a private key is a 256-bit number ...  
> **username_7**: It sounds like the real answer is risk/reward as perceived by the manufactures. Some feel the risk of using 12 words is worth the reward of more customers because they feel that 1) 12 is secure enough and 2) they can get more customers because they would rather deal with half the words.  

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### Answer by username_1 on 2019-03-17. Score: 0

A bitcoin private key is 256 bits. So you would need about 24 words (bip39 draws from 2048 words) to equal that. (2048^24= about 3x10^79
2^256= about 1x10^77)


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### Answer by username_2 on 2019-03-18. Score: 0

Notice in the actual unsafe working examples below that:

1. 12 words utilizes 128 (4x32) bits of entropy
2. 18 words utilizes 192 (4x48) bits of entropy
3. 24 words utilized 256 (4x64) bits of entropy

Note the results below can be easily extended to 15 and 21 BIP 39 seed words.

`% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-32 | bx mnemonic-new`

**health boil host ostrich fire spike body solar collect harvest catalog crystal**

`% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-48 | bx mnemonic-new`

**health boil host ostrich fire spike body solar collect harvest catalog cup mix tattoo market festival sudden please**

`% echo -n "This is a VERY pooor low entropy brain wallet" | bx base16-encode | bx sha256 | cut -c 1-64 | bx mnemonic-new`

**health boil host ostrich fire spike body solar collect harvest catalog cup mix tattoo market festival sudden pony notable beach wide health original inform**

Also note the repetition of the BIP 39 words above.


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### Answer by username_3 on 2018-03-06. Score: -2

Well for starters that should exponentially increase the security of the password if anything else


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