Bitcoin wallet seed phrase with an optional (extended) passphrase
bitcointalk-seed-passphrase-explainer
- Organisation
- BitcoinTalk
- Evidence role
- Community discussion
- Published
- 2026-08-04
- Source changes
- 0
- Detected differences
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- Unreviewed
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- Copies held
- 1
UchihaSarada writing an incident-motivated explainer on seed entropy and optional passphrases, arguing a passphrase cannot repair a weakly generated seed. The post links coinkite-mk3-advisory and coinkite-backgrounder, quotes btcsessions-passphrase-loss-report as evidence a passphrase alone does not protect a weak Mk3 seed, and points to the megathread bitcointalk-large-scale-compromise-thread. An educational community response with no replies at registration. The technical claims are the poster's own and those of the sources it cites, not verified here.
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Bitcoin Forum Bitcoin => Bitcoin Discussion => Topic started by: UchihaSarada on August 04, 2026, 03:37:20 AM Title: Bitcoin wallet seed phrase with an optional (extended) passphrase Post by: UchihaSarada on August 04, 2026, 03:37:20 AM This hack is a first time ever hardware wallet hack at this scale. Large-scale Coldcard compromise (1360.23 BTC stolen so far) (https://bitcointalk.org/index.php?topic=5589927.0) Technical details and some reported cases before and after this hardware wallet hack. https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/ https://blog.coinkite.com/entropy-technical-backgrounder/ Cracking Unsafe Bitcoin Wallets + Coldcard Mk4 Warning (Insecure Dice Based Seeds & Private Keys) (https://www.youtube.com/watch?v=oj_W3xOlt6U) https://www.reddit.com/r/Bitcoin/s/NJXFF7hI0a https://x.com/Zenul_Abidin/status/2083756420843839872 In Bitcoin, there are two main ways of storing your coins, with hot wallets and cold wallets. Cold wallets are best like hardware wallets and Coldcard is a hardware wallet. Wallets beyond hot and cold, are also classified as open-source and close source. Security advice is prioritizing open-source wallets over close-source wallets but it does not make a bad hardware open-source wallet is secure. Wallet seed phrases need to be created in a secure way and the hack on Coldcard wallet is because of their manufacturer broke this security principle, and ignored warnings from community in recent years. The most common reminder is "Not your keys, not your coins" but it's not enough as we all saw with Coldcard hardware wallet hack since days ago. It's still a good time to remind people about this, again but it's worth to do so. Reminder: do not keep your money in online accounts. (https://bitcointalk.org/index.php?topic=5421039.0) Bitcoin Q&A: Not your keys, not your coins. (https://www.youtube.com/watch?v=AcrEEnDLm58) Wallet: DOs and DON'Ts. (https://www.chainsec.io/checklist) From Coldcard hack, the importance of passphrase (extended custom phrase/ words) is known more and it's time to dive into it for learning before applying it for your Bitcoin wallet creation, backup, and storage. Before diving into it, there is another reminder. Firstly read below. Quote from: https://x.com/BTCsessions/status/2084024733511921691 IMPORTANT UPDATE: We just had our first confirmed loss of a Mk3 + 2 Word Passphrase. Drained at 2pm Aug 2nd Australia Time - Roughly 17hrs ago. -- @BTCsessions That post means only a passphrase is not enough to secure your wallet if the wallet seed phrase was created too weakly for example by Coldcard. You can read this test and report from Jameson Lopp to understand further about it. How many Bitcoin seed phrases are only one repeated word? (https://blog.lopp.net/how-many-bitcoin-seed-phrases-are-only-one-repeated-word/) Clearly nobody will use such Bitcoin wallet seed phrases but I want to use it for reminding that with such weak wallets, if you add any passphrase (extended/ custom words), it won't be too much helpful because it won't repair weak wallet seed phrase that was created with not enough dice rolls for strong entropy like 128 bits or 256 bits. What is entropy and how does Trezor generate your wallet? (https://trezor.io/guides/trezor-devices/trezor-fundamentals/what-is-entropy-and-how-does-trezor-generate-your-wallet) Generating entropy. (https://github.com/bitcoinbook/bitcoinbook/blob/develop/ch05_wallets.adoc#generating_entropy_and_encoding) (http://) | Entropy | Checksum (bits) | Entropy + checksum (bits) | Recovery code words | |128|4|132|12|Excerpt only. The complete copy is held offline and backs quotations on this site. The original publication remains the canonical public source.
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