Strong Master Passphrases Explained
By Mihaly Kertesz · Updated
A strong master passphrase relies on unique, unpredictable choices. A familiar quotation does not have the same generation model as independently selected random words, even at the same length. Memorability and an available recovery record affect whether that protection remains usable.
Master passphrases and offline guessing
An online service can rate-limit guesses. A copied encrypted vault may allow offline attempts under its format and key-derivation settings. A long generated passphrase improves resistance within those assumptions but does not protect an unlocked compromised device.
Reuse for email or another service links the vault credential to an unrelated leak. A dedicated master passphrase separates those exposures.
Random words in master passphrases
A generator with a documented method or physical dice with a published list provides an explicit selection process. Familiar quotations, songs and personal details do not provide independent sampling. Memory associations formed after generation differ from changing the words into a predictable sentence.
EFF publishes dice-based guidance and wordlists. Passary’s word tool uses browser randomness and its own 864-word list, rather than EFF’s 7,776-word list.
EFF random-passphrase guidance · Passary’s word-based generator
Master passphrase word counts and entropy
Uniform independent selection depends on both word count and list size. Eight selections from 864 words yield about 78 bits of randomness; six from 7,776 words yield about 77.5 bits. These estimates describe generation, rather than a particular attacker’s cracking time.
A known fixed separator adds no selection uncertainty. Predictable character substitutions are different from additional independently random choices.
| Uniform random selection model | Approximate randomness |
|---|---|
| 6 words from 864 choices | 58.5 bits |
| 8 words from 864 choices | 78 bits |
| 6 words from 7,776 choices | 77.5 bits |
Master passphrase memorability and typing
A practice vault can reveal keyboard-layout, spacing and punctuation differences across devices. Repeated entry from a protected record and later recall illustrate memorability without changing the generated phrase.
During a real credential change, an independent encrypted generation and its matching credentials preserve the earlier recovery path until the changed vault is confirmed.
Master passphrase recovery records
A sole record inside the vault it unlocks is unavailable during lockout. A protected physical record or separate encrypted location provides another boundary. Required keyfile and backup locations remain part of the recovery set.
Older backups may still require an earlier passphrase. Download pages and support cannot reconstruct missing cryptographic factors from the encrypted contents.
Backup generations and matching credentials · Passary recovery limits
Master passphrase changes
Exposure, reuse, weak selection and planned credential updates are reasons a passphrase may change. Applicable organizational policy can also determine requirements. Each change creates a new recovery state.
The saved vault, protected credential record and backup generations need matching factors. Device enrollment remains separate from durable credential-based access.