<p>To generate 12 words mnemonic, you have to seed 128bits(16bytes). It's not a recommendation but rule.</p>
<p>Below is detailed explanation from <a href="https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki" rel="nofollow noreferrer">BIP39</a>.</p>
<blockquote>
<p>The mnemonic must encode entropy in a multiple of 32 bits. With more entropy security is improved but the sentence length increases. We refer to the initial entropy length as ENT. The allowed size of ENT is 128-256 bits.</p>
</blockquote>
<blockquote>
<p>First, an initial entropy of ENT bits is generated. A checksum is
generated by taking the first ENT / 32 bits of its SHA256 hash. This
checksum is appended to the end of the initial entropy. Next, these
concatenated bits are split into groups of 11 bits, each encoding a
number from 0-2047, serving as an index into a wordlist. Finally, we
convert these numbers into words and use the joined words as a
mnemonic sentence.</p>
</blockquote>
<blockquote>
<p>The following table describes the relation between the initial entropy
length (ENT), the checksum length (CS), and the length of the
generated mnemonic sentence (MS) in words.</p>
</blockquote>
<blockquote>
<pre><code>CS = ENT / 32
MS = (ENT + CS) / 11
|  ENT  | CS | ENT+CS |  MS  |
+-------+----+--------+------+
|  128  |  4 |   132  |  12  |
|  160  |  5 |   165  |  15  |
|  192  |  6 |   198  |  18  |
|  224  |  7 |   231  |  21  |
|  256  |  8 |   264  |  24  |
</code></pre>
</blockquote>

CC BY-SA 4.0
2024-06-18T07:27:17.373Z
2024-06-18T07:27:17.373Z
Hyunhum Cho
<p>If I wanted to generate a 12 word mnemonic, how many additional bytes of entropy is recommended I use?</p>

CC BY-SA 4.0
2021-05-15T17:16:10.310Z
How do you mean "additional"? The words are your entropy.
Pieter Wuille
CC BY-SA 4.0
2021-05-15T20:01:28.063Z
To note: you should **not** choose your words, you should generate entropy in as random a way as possible, and then that entropy will be encoded into a mnemonic seed phrase. Humans are very bad/unreliable sources of entropy!
chytrik
CC BY-SA 4.0
2021-05-21T12:36:10.510Z
Sorry I meant in total how much entropy is considered secure for generating the mnemonic phrase?
Chiru
<private-key><mnemonic-seed>
How many bytes of entropy are recommended for seeding a mnemonic phrase?
Chiru
# How many bytes of entropy are recommended for seeding a mnemonic phrase?

(Asked by: username_0 on 2021-05-15)

If I wanted to generate a 12 word mnemonic, how many additional bytes of entropy is recommended I use?

**Tags:** private-key, mnemonic-seed

> **Comments:**
> **username_1**: How do you mean "additional"? The words are your entropy.  
> **username_2**: To note: you should **not** choose your words, you should generate entropy in as random a way as possible, and then that entropy will be encoded into a mnemonic seed phrase. Humans are very bad/unreliable sources of entropy!  
> **username_0**: Sorry I meant in total how much entropy is considered secure for generating the mnemonic phrase?  

---

## 1 answers

### Answer by username_3 on 2024-06-18. Score: 1

To generate 12 words mnemonic, you have to seed 128bits(16bytes). It's not a recommendation but rule.

Below is detailed explanation from [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki).

> The mnemonic must encode entropy in a multiple of 32 bits. With more entropy security is improved but the sentence length increases. We refer to the initial entropy length as ENT. The allowed size of ENT is 128-256 bits.

> First, an initial entropy of ENT bits is generated. A checksum is
> generated by taking the first ENT / 32 bits of its SHA256 hash. This
> checksum is appended to the end of the initial entropy. Next, these
> concatenated bits are split into groups of 11 bits, each encoding a
> number from 0-2047, serving as an index into a wordlist. Finally, we
> convert these numbers into words and use the joined words as a
> mnemonic sentence.

> The following table describes the relation between the initial entropy
> length (ENT), the checksum length (CS), and the length of the
> generated mnemonic sentence (MS) in words.

> ```
> CS = ENT / 32
> MS = (ENT + CS) / 11
> |  ENT  | CS | ENT+CS |  MS  |
> +-------+----+--------+------+
> |  128  |  4 |   132  |  12  |
> |  160  |  5 |   165  |  15  |
> |  192  |  6 |   198  |  18  |
> |  224  |  7 |   231  |  21  |
> |  256  |  8 |   264  |  24  |
>
> ```


---

