Data Recovery Case File · Mac & Apple Systems · The Interruption Hit the Encryption

An Interrupted Copy Can Damage the Structures That Make a Volume Readable at All

His enquiry describes a fault created by the transfer that was meant to preserve things. An old system drive placed in an external enclosure to copy files across, where "after copying some files it randomly disconnected — now it says the volume cannot be unlocked, and reinstalled internally it no longer starts." On an encrypted volume the interruption is more serious than on an ordinary one, because the structures that were damaged are the ones that make the rest interpretable.

The decode: what the disconnection damaged, and why the machine now rejects it

Why an encrypted volume has an extra dependency: alongside the data it holds structures recording how the encryption is arranged — the keys as stored, the parameters, and the records that let the correct credential open it. Those are small and they are essential, because without them the rest is unreadable regardless of whether the credential is known.

Why an interruption can damage them: those structures are read and updated during access. A device disconnecting mid-operation can leave an update half-applied, and a partially written encryption record does not describe a volume that can be opened.

Why that produces exactly the message he sees: the system reads the volume, recognises it as encrypted, and finds the unlocking structures inconsistent. "Cannot be unlocked" describes a failure to interpret rather than a rejected credential — which is worth distinguishing, because it is not that his password is wrong.

Why the drive itself is very likely fine: the fault is in what is stored rather than in the storing. A solid-state drive that copied files successfully until the moment of disconnection was working, and nothing since suggests the device has failed.

Why the enclosure is the likely culprit for the disconnection: third-party enclosures vary considerably in how reliably they sustain a connection under load. A copy is exactly the sustained demand that surfaces a marginal one, and the drive dropping mid-transfer is a connection failure rather than a device failure.

Why the machine rejects it internally now, and this is a separate matter: a drive refitted after being removed may no longer satisfy the checks the machine performs on its startup device. That is a question about the machine's expectations rather than about the drive's health, and it does not affect whether the data can be read elsewhere.

Why the repair utility failing is fortunate: it could not repair the volume, so it did not write to it. An automated repair on damaged encryption structures can discard records rather than reconstruct them, and its inability to proceed preserved the position.

What is done instead: the drive is imaged at the block level exactly as it stands, encrypted content and all. Every subsequent attempt runs against the image, so the structures can be examined and reconstructed without further risk to the original.

What makes reconstruction possible: encryption arrangements of this kind typically keep more than one copy of their key structures. Where the primary set was damaged at the moment of interruption, a secondary set frequently survives — and with the owner's credential, the volume then opens from the image.

What must not happen: no further repair attempts, and no reformatting when a machine offers. The credential is only useful while the structures it operates on still exist.

On the bench

Encryption metadata damage was distinguished from device failure — an encrypted volume holding small structures recording key storage and parameters, without which content is uninterpretable regardless of credential, and those structures being read and updated during access so that disconnection can leave an update half-applied. An unlock failure of this kind indicates failure to interpret rather than a rejected credential. No repair utility was permitted to write to the volume, and primary and secondary encryption structures compared from a block-level image.

The outcome

Metadata damage distinguished from device failure, no repair permitted, and the volume decrypted from a block-level image using the owner's credential. Free assessment, one fixed written figure including VAT; where a chip has to be removed, 50% of parts and labour is payable upfront with the balance only on success — otherwise no recovery, no fee. The decode: your password is not being rejected. The structures that let it open the volume were damaged when the connection dropped mid-copy — and encryption arrangements usually keep a second copy of those.

Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.