Open a .crypto file on macOS
A .crypto file is an encrypted container made by Encrypto, a free tool
from MacPaw. Someone encrypted a file or folder, set a password, and sent you
the result.
Most pages describing this format will tell you that only Encrypto can open
one. That isn’t true. Purrchiver reads .crypto files directly — and
reading them is free.
Two things that open it
Encrypto (free, from MacPaw)
The original tool. Free for Mac and Windows, and if you only ever expect to
see one .crypto file, installing it is a perfectly good answer. We’d rather
say that plainly than pretend otherwise.
Purrchiver
Drop the .crypto file on Purrchiver and it prompts for the password, then
opens the decrypted contents so you can browse and extract them like any
archive. Useful when the .crypto file is one item in a pile of mixed
archives — you handle all of them in one place instead of installing a
single-purpose app.
Two details that matter in practice:
- Purrchiver shows the sender’s password hint. Encrypto lets the sender store an optional hint inside the file. Purrchiver reads that hint without decrypting anything and shows it on the password prompt — so if you’re guessing, you get the same nudge the sender intended.
- Opening and decrypting are free. No unlock, no subscription. If someone
sent you a
.cryptofile, you don’t have to pay anything to read it.
Purrchiver cannot create .crypto files. It is deliberately read-only for
this format. If you want to send someone an encrypted file, use
age encryption or an
encrypted ZIP — both open on more machines than
.crypto does.
What the file actually is
Encrypto’s container is identified by the magic bytes MPE1. Inside, the
payload is AES-256 encrypted with a key derived from the sender’s password,
and both the file directory and every file in it carry an HMAC.
Purrchiver verifies those HMACs as it extracts. That has a practical
consequence worth knowing: a .crypto file that has been corrupted or
altered in transit fails loudly rather than handing you damaged files. The
three failure modes are distinct — wrong password, tampered contents, and
“this isn’t actually a .crypto file” are separate errors, so you can tell a
bad password from a bad download.
Nothing is written to disk until verification passes. A wrong password or a failed HMAC releases no plaintext at all.
If it won’t open
- “Wrong password.” The password is the sender’s, not anything you set. Check the hint on the prompt — it may be there.
- “Not a .crypto file.” Check the file actually arrived intact. Run
file yourfile.cryptoin Terminal; a truncated download is common when the file came through a webmail attachment limit. - “Tampered.” The HMAC didn’t verify. The file was altered or corrupted after it was created — ask the sender to send it again, ideally through something that doesn’t re-encode attachments.
- You don’t have the password. There’s no recovery path. AES-256 with a password-derived key is not brute-forceable in any useful timeframe. Ask the sender.
What else Purrchiver opens
The reason to reach for Purrchiver instead of a single-format tool is that
.crypto is rarely the only odd thing in the folder:
| You have | Purrchiver |
|---|---|
.crypto (Encrypto) | Opens, free |
.age | Opens and creates — see age encryption |
| Encrypted ZIP / 7z (AES-256) | Opens and creates |
| Encrypted RAR | Opens |
| Encrypted DMG | Opens |
.zip .rar .7z .tar.* .iso .dmg .cpio | Opens |
Purrchiver is free to download and free to extract anything, including every encrypted format above. The one-time $9.99 unlock covers creating encrypted archives — not opening them.
Get Purrchiver on the Mac App Store →
Related
- Encrypted archives — the full encryption picture across every format
- age encryption on macOS — the modern way to send someone an encrypted file
- Privacy & security — why nothing Purrchiver does touches the network
- Format support — the complete read/write matrix