Purrchiver creates encrypted archives with AES-256 — the same algorithm 7-Zip and WinRAR use. Every encrypted archive is verified after creation: Purrchiver re-opens the archive, reads each entry, and confirms the password unlocks it. You will never distribute an archive that no one can open.
Creating an encrypted archive
In the Create Archive sheet, tick Encrypt with AES-256. Two fields appear:
- Password — the password you’ll need to open the archive later.
- Confirm password — type it again. The Create button stays disabled until both fields match.
Below the password field, a strength meter tells you how strong your password is:
The strength meter is local-only — no network requests, no AI, no SDK. It’s a small heuristic that checks length, character classes, common-password patterns, and repetition.
Why the confirm field is non-optional
A single password field with no confirmation is how people accidentally encrypt archives with a typo’d password — and then can’t open them later. Purrchiver doesn’t ship that failure mode.
What “verified after creation” means
When you click Create (with the default verify-after-creation setting):
- Purrchiver writes the encrypted archive.
- Purrchiver immediately re-opens it.
- Purrchiver decrypts every entry end-to-end with your password, exercising the cipher across the whole archive — not just a probe of the first few entries.
- If decryption fails (which it shouldn’t, but if), Purrchiver shows an error and the partially-written archive is removed. Your source files are unaffected.
The verify-after-creation behavior is configurable in Settings → Compression. The default is Smart (verify every encrypted archive, and every unencrypted archive smaller than 500 MiB). You can also force Always, restrict to Encrypted only, or turn it off with Never — in which case verification is skipped and the archive is whatever bytes landed on disk.
In practice verification always passes; the step is how you know it does.
Opening an encrypted archive
When you open an encrypted archive, Purrchiver shows a password prompt before listing the contents:
Type the password and click Open. If the password is wrong, Purrchiver tells you specifically:
Incorrect password. Try again.
…not the unhelpful “extraction failed” that some tools show. Wrong-password is a known case and gets its own error.
How long the password sticks
Passwords stay in memory for the open session only — Purrchiver doesn’t persist them between launches. Close the archive and the password is gone.
There is no Purrchiver password file, no preferences entry, no SQLite database, no Keychain entry.
Changing the password on an existing archive
The fast-path Save (⌘S) in Edit mode reuses the active preset’s password — it does not surface password fields. To change the password, add encryption to a previously-unencrypted archive, or remove encryption, use the full Create Archive sheet from Edit mode instead:
- Open the archive, enter Edit mode, enter the current password if prompted.
- Use Create Archive (not the fast-path ⌘S Save) to open the full sheet with format + encryption controls.
- Pick an encrypted variant (ZIP + AES-256 or 7z + AES-256), or an unencrypted variant to drop encryption.
- Enter the new password (with confirmation) if encrypting.
- Save to a new filename, verify it opens with the new password, then delete the old archive.
Purrchiver writes a new archive with the new settings. The save writes directly to the destination you pick in the Save panel — see Editing an existing archive for the data-safety note about saving over an original.
Password best practices
- Use a passphrase, not a password. Four random words (“correct
horse battery staple”) beats a 10-character
Pa$$w0rd!by orders of magnitude. The strength meter rewards length more than complexity. - Don’t reuse passwords. Especially not your email or banking password. If the archive falls into the wrong hands, you don’t want their next attempt to be your bank.
- Use a password manager. Purrchiver doesn’t store passwords — once you close the archive, the password is gone. Generate and store the password in 1Password / Bitwarden / Apple Passwords / Keychain Access, and paste it when prompted.
v1.0 password limitations
- ASCII characters only. Letters A–Z (upper and lower case), digits 0–9, and standard punctuation. The Create Archive sheet rejects passwords containing accented characters, ideographs (CJK), emoji, or any other non-ASCII glyph. Older archive engines disagree on which Unicode encoding to use for non-ASCII passwords, so an archive made with one tool often won’t open with another. Lifting the gate is on the v1.1 roadmap once the engine round-trips Unicode reliably.
- No NUL bytes or control characters. The compose field rejects these because most archive formats can’t represent them consistently.
- Length matters more than complexity. A 16-character random string is dramatically stronger than an 8-character one with punctuation tricks, even within the ASCII-only constraint.
What encryption Purrchiver supports
| Format | Read encrypted | Write encrypted |
|---|---|---|
| ZIP + AES-256 | ✓ | ✓ |
| ZIP + ZipCrypto (legacy) | ✓ (read only) | ✗ — see below |
| 7z + AES-256 | ✓ (content + header-encrypted) | ✓ |
| RAR encrypted | ✓ (content + header-encrypted, via UnRAR) | ✗ — Purrchiver can’t write RAR at all |
Why no ZipCrypto write?
ZipCrypto is the legacy ZIP encryption scheme. It has been trivially
breakable since the late 1990s — academic papers in 1994 demonstrated
practical key-recovery attacks. Modern ZIP-cracking tools (zip2john,
john) crack ZipCrypto-encrypted archives on a laptop in seconds.
Purrchiver reads ZipCrypto-encrypted archives (you’ll encounter them
in old .zip files from the 90s/2000s), but it doesn’t write them —
because shipping known-broken crypto as a creation option would be
irresponsible. If you need to encrypt a ZIP, Purrchiver uses AES-256.
What encryption protects (per format)
| Format | What encryption covers |
|---|---|
| ZIP + AES-256 | File contents only. Filenames inside the archive remain visible to anyone listing the archive. |
| 7z + AES-256 | File contents AND filenames. If you need to hide what’s in an encrypted archive, use 7z. |
| RAR encrypted (read only) | Both content-encrypted and header-encrypted variants supported for extraction. |
For 7z, Purrchiver encrypts both file contents AND filenames whenever you pick the 7z + AES-256 format. There is no separate “encrypt filenames” toggle in v1.0 — header-encryption is on for every 7z you encrypt. (Content-only 7z encryption, leaving filenames visible, is on the v1.1 list if anyone needs it; tell us at corey@purrchiver.app.)
What Purrchiver doesn’t do with passwords
- Purrchiver does not send your password anywhere. Ever. There is no network connection.
- Purrchiver does not keep a password file, preferences entry, or database. Nothing persists between launches.
- Purrchiver does not have a “forgot password” feature. There is no way to recover a password you’ve forgotten — encryption is one-way by design. If you forget, the data is gone.
Related
- Creating a new archive
- Editing an existing archive — Edit mode + the Create Archive sheet
- Privacy & security — verifiable claims about what Purrchiver does and doesn’t access
- Common errors — what each password error means