Hidden Line Feed Character Blocks Bitcoin Core Wallet Access
SurvivedWallet passphrase was unavailable — a recovery path existed and access was restored.
In February 2017, scutzi128 documented a Bitcoin Core wallet access failure on the Bitcoin Technical Support forum. The user had encrypted their wallet with a 25-character random passphrase generated in Microsoft Excel, then copied it into Bitcoin Core's encryption dialog. Multiple backups of the encrypted wallet.dat file existed, but the passphrase itself was not backed up—the user assumed it was safe because it was only stored in their own systems.
Months later, when the user attempted to unlock the wallet, the stored passphrase no longer worked. Initial investigation revealed the cryptographic search space was computationally infeasible: 36^25 possible combinations (8.08 × 10^38), requiring an estimated 1.28 × 10^22 years to brute-force at one billion attempts per second. The user then located the passphrase on an old system backup and re-entered it into Bitcoin Core—but it was still rejected.
Using the btrecover tool with wildcard parameters, the root cause was identified: a line return/line feed character (invisible to the human eye) had been appended to the passphrase during the copy-paste operation from Excel to the wallet encryption dialog. This hidden control character—likely introduced by Excel's automatic formatting, smart quote substitution, or clipboard behavior—was cryptographically significant and prevented the correct passphrase from validating.
Forum members (including achow101 and DannyHamilton) confirmed that Microsoft Office products frequently inject invisible characters including smart quotes, ligatures, and control characters. Once the line feed character was identified and removed, the user successfully unlocked the wallet and accessed their Bitcoin. The incident resolved by February 22, 2017. The case demonstrates a custody failure rooted in passphrase handling methodology and backup practices rather than platform or systemic cryptocurrency failure.
| Stress condition | Passphrase unavailable |
| Custody system | Software wallet |
| Outcome | Survived |
| Documentation | Present and interpretable |
| Year observed | 2017 |
| Country | unknown |
Why passphrases fail years after they are set
The failure mode documented consistently across observed cases is temporal: the passphrase is set with confidence, not used for an extended period, and then cannot be reproduced exactly when needed. A single character difference — different capitalization, an added space, a slightly different special character — produces a different wallet with a zero balance. The holder may be certain they remember the passphrase while being unable to produce the exact string that was originally set.
What makes this particularly difficult is that there is no signal at the moment of failure. A wrong passphrase does not produce an error message. It opens an empty wallet. The holder sees a zero balance and typically concludes the passphrase was wrong — but without knowing which part was wrong, or by how much.
Professional passphrase recovery services can attempt permutations when the holder has partial information: they remember the general structure, typical patterns they use for passwords, the approximate length, or that it included a specific word. Recovery from total non-recollection is not feasible.
The preventive action is to store a passphrase record — not with the seed phrase, which would defeat its security purpose, but in a separate secure location accessible to the holder and potentially a designated recovery person. A passphrase that exists only in memory has a time horizon: it will eventually be forgotten, and the timing is unpredictable.
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