<p>If it is easy to remember, it is almost certainly easy to guess.</p>

<p>And by guess, I don't mean a single person trying a few sentences in some time. I mean exposing yourself to a brute force attack by the entire world (the block chain data is public), for eternity.</p>

CC BY-SA 3.0
2014-03-13T18:11:34.770Z
I agree and the example I gave is probably too obvious. But maybe a randomly chosen sequence of words followed by a checksum is strong enough?

Consider this example: `5HumanPerfumeLatticeDeceiveCementRuneHydrogenDGA1s5`
uminatsu
CC BY-SA 3.0
2014-03-13T18:59:47.800Z
If you're doing that, you might as well remember seven words generated at random and hash them with a standard algorithm to generate the key. It would take less effort than remembering the checksum.
Diego Basch
CC BY-SA 3.0
2014-03-13T19:28:49.973Z
Pretty much anything a human can even come up with (except when using diceware, ...) has only a fraction of the entropy that is assumed by the cryptography.
Pieter Wuille
CC BY-SA 3.0
2014-03-13T17:59:30.427Z
2014-03-13T17:59:30.427Z
Pieter Wuille
<p>A series of random words (not a sentence!) <a href="https://electrum.org/seed.html" rel="nofollow">long enough</a> to use as a secure key should be about 12 words long, which could be around 100 characters long (figuring they're fairly long, 7-8 average, with a space in between). This gives you 2^128 combinations that you might have to try to crack your password, which might take about <a href="http://www.eetimes.com/document.asp?doc_id=1279619" rel="nofollow">1 billion billion years</a>.</p>

<p>A private key, in base 58 format, <a href="https://en.bitcoin.it/wiki/Private_key" rel="nofollow">is 51 characters</a> long. Your idea of using a 51-character sentence as a private key would probably give about <a href="https://en.wikipedia.org/wiki/Entropy_%28information_theory%29" rel="nofollow">51 bits of entropy</a> (English is around 0.6 to 1.3 bits per character), which could be cracked in about 12.5 seconds.</p>

CC BY-SA 3.0
2014-03-13T18:37:51.173Z
2014-03-13T18:37:51.173Z
Tim S.
<p>A brain wallet usually applies a hash function on a passphrase to derive the private key. But what if the private key itself is memorable and we just use the private key as the brain wallet?</p>

<p>For example it is very easy to memorize this private key:</p>

<pre><code>Private key: 5JustSomeVeryEasyToRememberBitcoinPrivateKeyWALEmag
Address: 1GtAW7vntpij1q8Mqi3FQw8R1gAd9rnRV4
</code></pre>

<private-key><brain-wallet>
What if the brain wallet is just a memorable private key itself?
uminatsu
# What if the brain wallet is just a memorable private key itself?

(Asked by: username_0 on 2014-03-13)

A brain wallet usually applies a hash function on a passphrase to derive the private key. But what if the private key itself is memorable and we just use the private key as the brain wallet?

For example it is very easy to memorize this private key:

```
Private key: 5JustSomeVeryEasyToRememberBitcoinPrivateKeyWALEmag
Address: 1GtAW7vntpij1q8Mqi3FQw8R1gAd9rnRV4

```

**Tags:** private-key, brain-wallet


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## 2 answers

### Answer by username_3 on 2014-03-13. Score: 4 | Accepted answer

A series of random words (not a sentence!) [long enough](https://electrum.org/seed.html) to use as a secure key should be about 12 words long, which could be around 100 characters long (figuring they're fairly long, 7-8 average, with a space in between). This gives you 2^128 combinations that you might have to try to crack your password, which might take about [1 billion billion years](http://www.eetimes.com/document.asp?doc_id=1279619).

A private key, in base 58 format, [is 51 characters](https://en.bitcoin.it/wiki/Private_key) long. Your idea of using a 51-character sentence as a private key would probably give about [51 bits of entropy](https://en.wikipedia.org/wiki/Entropy_%28information_theory%29) (English is around 0.6 to 1.3 bits per character), which could be cracked in about 12.5 seconds.


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### Answer by username_1 on 2014-03-13. Score: 3

If it is easy to remember, it is almost certainly easy to guess.

And by guess, I don't mean a single person trying a few sentences in some time. I mean exposing yourself to a brute force attack by the entire world (the block chain data is public), for eternity.

> **Comments:**
> **username_0**: I agree and the example I gave is probably too obvious. But maybe a randomly chosen sequence of words followed by a checksum is strong enough?  Consider this example: `5HumanPerfumeLatticeDeceiveCementRuneHydrogenDGA1s5`  
> **username_2**: If you're doing that, you might as well remember seven words generated at random and hash them with a standard algorithm to generate the key. It would take less effort than remembering the checksum.  
> **username_1**: Pretty much anything a human can even come up with (except when using diceware, ...) has only a fraction of the entropy that is assumed by the cryptography.  

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