Understand custody · Human randomness
Why a Phrase from Memory Made a Bad Wallet
The brainwallet idea sounded elegant: remember a phrase and recover a key anywhere. The flaw was that people choose words far less randomly than they believe.
A wallet without a file
In simple brainwallets, the same phrase always produced the same private key. There was no file to keep—only a sentence to remember.
Quotations, lyrics, dates, and familiar combinations repeat across people. Convenience moved all security into human choice.
The hunt began in advance
Researchers tested about 300 billion candidates. Excluding their experiments, they found 884 used brainwallets; all but 21 were drained, often within a day and sometimes within minutes.
Likely phrases could be converted to addresses, monitored, and swept automatically after funding.
Why a generated seed is different
A modern mnemonic also uses words, but a wallet should derive them from machine-generated randomness. The words encode entropy that already exists.
A self-written sentence does not become safe because it is long or personally meaningful.
A secret that is easy for a person to invent is often easy for a machine to enumerate.
Sources and verification
This article contains no usable secret phrases. Never enter a seed phrase into a website or message.
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