Glossary

The software pages mention checksums, encryption, licences. These words have a precise meaning, and you don't need to be a programmer to understand it. Here is what they mean, and why they matter to you.

SHA-256 checksum

A string of 64 characters computed from the exact contents of a file. Change a single byte of the file and the checksum changes entirely. Every software page shows the checksum of the published program: if the one of the file you downloaded is identical, it is that very file, intact. If it differs, don't open it.

How to get a file's checksum on Windows

1. Open PowerShell (right-click the Start button → “Terminal” or “Windows PowerShell”).
2. Type Get-FileHash .\Downloads\Coffre.exe, replacing the path with your file's, then press Enter.
3. Compare the displayed value with the one on the software page. Upper and lower case don't matter; any other difference does.

Encryption

Transforming data so that it cannot be read without a key. A stolen encrypted file gives nothing away: without the key, it is just noise. Coffre encrypts your vault on your disk; the key is derived from your master password and is never written anywhere.

AES-256-GCM

The encryption algorithm Coffre uses. AES is the standard adopted by governments and banks; “256” is the key size, beyond the reach of any brute-force attack; “GCM” adds a seal that detects any change to the encrypted contents, even a single byte.

Key derivation (scrypt)

The computation that turns your master password into an encryption key. It is deliberately slow and memory-hungry: a fraction of a second for you when opening the vault; years for anyone trying millions of passwords. That is what makes a reasonable master password genuinely strong.

Password hashing (argon2id)

What the member area does with your password: it is never stored. Only a slow-to-compute, impossible-to-reverse fingerprint of it is kept. Even if the database leaked, your password would not be in it.

Perceptual hash (dHash)

A summary of what an image looks like, not of its bytes. Two nearly identical photos — one recompressed, resized or slightly cropped — have close hashes, where their SHA-256 checksums would be completely different. That is how PhotoTri finds the duplicates a simple size-based sort would miss.

MIT licence

The free licence of all 7 programs. It lets you use, copy, modify and redistribute them, commercially included, on one condition: keep the author's notice. It gives no warranty — true of every free licence, and written in it.

Local (no cloud)

Your data stays on your computer. No server receives it, no account is needed, nothing syncs behind your back. The flip side is accepted: if you lose your disk without a backup, nobody can give it back to you.