Will all 24 words of a seed-phrase be unique by specification? Or is it possible for a word to occupy two positions (ie the word "tool" is #8 AND #20 in a valid, securely generated seed)
Welcome to Bitcoin Stack Exchange
Bitcoin is a question and answer site for Bitcoin users and enthusiasts. It's built and run by you as part of the Stack Exchange network of Q&A sites. With your help, we're working together to build a library of detailed answers to every question about technologies supporting the Bitcoin currency in the past, present, or future.
Please direct questions specific to other cryptocurrencies at their respective sites:
EOS,
Ethereum,
IOTA,
Monero,
Stellar,
Tezos
We're a little bit different from other sites. Here's how:
Ask questions, get answers, no distractions
This site is all about getting answers. It's not a discussion forum. There's no chit-chat.
Just questions...
...and answers.
up vote
Good answers are voted up and rise to the top.
The best answers show up first so that they are always easy to find.
accept
The person who asked can mark one answer as "accepted".
Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.
Does BIP39 mnemonic construction avoid repeating words?
up vote
14
down vote
favorite
asked Sep 24 '17 at 0:20
pinhead
2,4662 gold badges14 silver badges28 bronze badges
2,4662 gold badges14 silver badges28 bronze badges
2 Answers
up vote
4
down vote
accept
There is nothing stopping a word to be repeated more than once. In a 24 word mnemonic, with 2048 possible words in the dictionary (BIP 39), there is a probability of at least one duplicate around 12.7% of the time (variation of the birthday paradox).
answered Sep 24 '17 at 2:22
MeshCollider
8,8653 gold badges16 silver badges40 bronze badges
8,8653 gold badges16 silver badges40 bronze badges
up vote
3
down vote
No, the BIP39 construction does not avoid repeating words.
It is possible for a word to show up multiple times, but since there are 2048 words it is fairly unlikely for repeats to show up in randomly generated keys.
answered Sep 24 '17 at 2:16
G. Maxwell
6,2242 gold badges11 silver badges41 bronze badges
6,2242 gold badges11 silver badges41 bronze badges
Get answers to practical, detailed questions
Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.
Ask about...
- Specific issues with using Bitcoin
- Algorithms and concepts specific to Bitcoin
- Sourcecode of Bitcoin implementations and libraries
- Problems with developing Bitcoin applications
- General challenges faced by multiple currencies including Bitcoin
- On-going developments which may get adopted by Bitcoin in the future
- Research into Bitcoin
Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.
Questions that need improvement may be closed until someone fixes them.
Don't ask about...
- Anything not applicable to Bitcoin
- Investment advice or market values
- Site, tool, library, or software recommendations
- Topics that are primarily opinion-based
- Questions with too many possible answers or that would require an extremely long answer
Tags make it easy to find interesting questions
All questions are tagged with their subject areas. Each can have up to 5 tags, since a question might be related to several subjects.
Click any tag to see a list of questions with that tag, or go to the tag list to browse for topics that interest you.
Does BIP39 mnemonic construction avoid repeating words?
up vote
14
down vote
Will all 24 words of a seed-phrase be unique by specification? Or is it possible for a word to occupy two positions (ie the word "tool" is #8 AND #20 in a valid, securely generated seed)
asked Sep 24 '17 at 0:20
pinhead
2,4662 gold badges14 silver badges28 bronze badges
2,4662 gold badges14 silver badges28 bronze badges
You earn reputation when people vote on your posts
Your reputation score goes up when others vote up your questions, answers and edits.
+10
question voted up
+10
answer voted up
+15
answer is accepted
+2
edit approved
As you earn reputation, you'll unlock new privileges like the ability to vote, comment, and even edit other people's posts.
| Reputation | Privilege |
|---|---|
| 15 | Vote up |
| 50 | Leave comments |
| 125 | Vote down (costs 1 rep on answers) |
At the highest levels, you'll have access to special moderation tools. You'll be able to work alongside our community moderators to keep the site focused and helpful.
| 500 | Vote to close, reopen, or migrate questions |
|---|---|
| 1000 | Edit other people's posts |
| 2000 | Access to moderation tools |
Improve posts by editing or commenting
Our goal is to have the best answers to every question, so if you see questions or answers that can be improved, you can edit them.
Use edits to fix mistakes, improve formatting, or clarify the meaning of a post.
up vote
9
down vote
There is nothing stopping a word to be repeated more than once. In a 24 word mnemonic, with 2048 possible words in the dictionary (BIP 39), there is a probability of at least one duplicate around 12.7% of the time (variation of the birthday paradox).
answered Sep 24 '17 at 2:22
MeshCollider
8,8653 gold badges16 silver badges40 bronze badges
8,8653 gold badges16 silver badges40 bronze badges
Preventing duplicate words will in fact restrict the entropy of the seed phrase. - pim Oct 23 '17 at 14:34
Unlock badges for special achievements
Badges are special achievements you earn for participating on the site. They come in three levels: bronze, silver, and gold.
| Student | First question with score of 1 or more |
| Editor | First edit |
| Good Answer | Answer score of 25 or more |
| Civic Duty | Vote 300 or more times |
| Famous Question | Question with 10,000 views |
Sign up to get started
Signing up allows you to:
- Earn reputation when you help others with questions, answers and edits.
- Select favorite tags to customize your home page.
- Claim your first badge: Informed
Looking for more in-depth information on the site? Visit the Help Center
Bitcoin Stack Exchange is part of the Stack Exchange network
Like this site? Stack Exchange is a network of 174 Q&A sites just like it. Check out the full list of sites.
Use comments to ask for more information or clarify a question or answer.
You can always comment on your own questions and answers. Once you earn 50 reputation, you can comment on anybody's post.
Remember: we're all here to learn, so be friendly and helpful!