<p>Recently I setup a crypto wallet which used a 12-word BIP39 passphrase as security. I noticed something peculiar when I went to setup an additional wallet. The first and last words of the previous wallet I created were exactly the same on the new one. I thought this was odd so I created many more wallets to try and determine if that behavior was just a fluke.</p>
<p>On the next dozen or so wallets I didn't get the same first and last words again, although I did on occasion get one or the other. Next I took the original first and last word then input words randomly that were present in my other created wallets in slots 2-11 to see if the wallet would be valid; they were valid 100% of the time. For the last test I decided to take the first word of my original wallet and repeat it twelve times, which also produced a valid wallet.</p>
<p>Is this typical behavior BIP39 mnemonic passphrase cryptography? If not what would the cause be other than a botched implementation?</p>

CC BY-SA 4.0
2021-09-08T07:22:52.500Z
BIP39 mnemonics have a checksum. For 12-word mnemonics the checksum is 4 bits which means if you pick 12-words at random the mnemonic should be invalid 15/16 times. This looks like a bad implementation of BIP39
Mike D
CC BY-SA 4.0
2021-09-08T10:41:16.300Z
If you are asking about a specific implementation, please mention which one, so that we can avoid it.
Murch
CC BY-SA 4.0
2021-09-08T19:40:44.703Z
@MikeD, Thank you for confirming my suspicions; so for such an issue what would be the worst case scenario of this? I would imagine it would still be difficult to find a wallet that is in use already just because of the amount of possibilities, although I could be totally wrong on that.
Yoshi Miro
CC BY-SA 4.0
2021-09-08T19:43:57.703Z
@Murch, I'm going to report this to the developer right away since this obviously isn't the correct behavior. Once they have enough time to address or not it I'll report back as to what the token is that uses this dumpster fire to secure it's wallet.
Yoshi Miro
<mnemonic-seed>
Is this mnemonic cryptography flawed?
Yoshi Miro
# Is this mnemonic cryptography flawed?

(Asked by: username_0 on 2021-09-08)

Recently I setup a crypto wallet which used a 12-word BIP39 passphrase as security. I noticed something peculiar when I went to setup an additional wallet. The first and last words of the previous wallet I created were exactly the same on the new one. I thought this was odd so I created many more wallets to try and determine if that behavior was just a fluke.

On the next dozen or so wallets I didn't get the same first and last words again, although I did on occasion get one or the other. Next I took the original first and last word then input words randomly that were present in my other created wallets in slots 2-11 to see if the wallet would be valid; they were valid 100% of the time. For the last test I decided to take the first word of my original wallet and repeat it twelve times, which also produced a valid wallet.

Is this typical behavior BIP39 mnemonic passphrase cryptography? If not what would the cause be other than a botched implementation?

**Tags:** mnemonic-seed

> **Comments:**
> **username_1**: BIP39 mnemonics have a checksum. For 12-word mnemonics the checksum is 4 bits which means if you pick 12-words at random the mnemonic should be invalid 15/16 times. This looks like a bad implementation of BIP39  
> **username_2**: If you are asking about a specific implementation, please mention which one, so that we can avoid it.  
> **username_0**: @username_1, Thank you for confirming my suspicions; so for such an issue what would be the worst case scenario of this? I would imagine it would still be difficult to find a wallet that is in use already just because of the amount of possibilities, although I could be totally wrong on that.  
> **username_0**: @username_2, I'm going to report this to the developer right away since this obviously isn't the correct behavior. Once they have enough time to address or not it I'll report back as to what the token is that uses this dumpster fire to secure it's wallet.  

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## 0 answers

