The files you manage on Mnemonica are protected by a checksum-based integrity check: a system that lets you be certain every copy of a file is byte-for-byte identical to the master held on the platform. This article briefly explains what a checksum is, how the Mnemonica Gate verifies it automatically during transfers, and where to find it in the Vault.

What is a checksum?

A checksum (or digest) is a short fingerprint computed from a file's contents. If even a single byte changes, the checksum changes completely. By comparing the checksum of two copies we can tell with certainty whether they are identical or whether one has been corrupted along the way.

Mnemonica uses three algorithms, depending on the context:

• SHA-256 — the strongest, cryptographic fingerprint (64 hex characters); this is the value to use when verifying a file's integrity manually.
• xxHash64 — a fast, non-cryptographic fingerprint, used for the quick checks performed during transfers.
• CRC32C — a lightweight checksum used by cloud storage to detect transfer errors.

Automatic verification in Mnemonica Gate

Mnemonica Gate v 3.4.0 and above checks every transfer it runs, both uploads and downloads. There is nothing to switch on: verification is automatic and built in.

How it works. It's a two-party check: the Gate and the platform each compute the fingerprint of the same bytes independently, then compare them — neither side simply trusts a number reported by the other. The fingerprint is computed on the fly as the file streams past, so the overhead is minimal.

• Uploads — verified twice over: block by block during the upload (so corruption is caught early) and then on the whole file at the end.
• Downloads — verified on the whole file at the end. Older legacy media has no reference fingerprint and is therefore not checked.

There is no "passed" badge. A successful check is silent: the transfer simply completes and the row clears from the queue. The Gate only shows something when a check fails. In practice: an upload that finished with no badge passed verification; a clean download was either verified or was simply a legacy file with nothing to check against.

"Resuming — verifying…". If you pause and resume a transfer (or the Gate resumes one after a network hiccup or an app restart), you'll briefly see the Resuming — verifying… indicator: the Gate is re-reading the already-transferred bytes to pick the fingerprint back up from the right point. The progress bar isn't frozen, and no action is needed.

When a file is flagged

If the two fingerprints disagree at the end of a transfer, the Gate flags the file with an amber Integrity check failed label and an amber progress bar, on both the queue card and the file row.

This flag is advisory: the transfer still completed and the bytes were delivered, but the copy does not match the master and should not be trusted. The file is deliberately kept in the queue so that you decide how to proceed — the Gate does not re-transfer it automatically.

What to do:

• Download → the downloaded copy may be damaged: delete it and download it again.
• Upload → the copy the platform received does not match your local file: re-upload it.

Hovering the badge on the file row shows the two fingerprints side by side (local ≠ source). If the problem recurs across repeated attempts, contact support with the file name and both digests.

Flagged ≠ error. The amber flag means the bytes arrived but don't match. A genuine transfer error is shown in red and is retried automatically (for example, when an upload's block-level check fails).

Where to find checksums in the webapp

Beyond the Gate's automatic check, you can view the checksums stored for each file directly in the Works, in the Inspector panel.

Navigation path:

1. Open a Project from the Dashboard
2. Go to the Works tab
3. Open a Master, then a Version, and browse into its contents
4. Select an individual file (not a package or folder)
5. In the Inspector on the right, find the Checksum section near the bottom

The section shows one row per available algorithm (SHA-256, xxHash64, CRC32C). The value is truncated to fit the panel: hover to see the full fingerprint in a tooltip, or use the copy button to place the complete value on your clipboard.

The Checksum section appears only when you select a single file. Packages (DCP, IMF, Audio…) and folders have no checksum of their own: drill into the package and select the file inside it.

Verifying a download manually

To confirm that a downloaded file matches the master on Mnemonica:

1. In the Inspector, copy the file's SHA-256 value.
2. Compute the SHA-256 of your local copy:
   • macOS: shasum -a 256 <file>
   • Linux: sha256sum <file>
   • Windows (PowerShell): Get-FileHash <file> -Algorithm SHA256
3. Compare the two strings: if they match exactly, the file is intact; if they differ, the download is corrupt or incomplete and should be repeated.