Secure data destruction: erasure, degaussing and shredding are not interchangeable

What each method actually guarantees

Certified erasure

Software overwrites the media and verifies the result, device by device. It keeps the asset resaleable, which is the entire point. It depends on the drive reporting honestly, so it needs verification and a per-serial record. When a certificate of erasure is enough, and when only destruction will do, is its own question.

Degaussing

A magnetic field destroys the data and, in practice, the drive. It applies to magnetic media and does nothing to solid-state devices, a distinction that has ended more than one audit badly.

Physical destruction

Shredding or disintegration. Unambiguous, irreversible, and it forfeits all recovery value. Particle size matters and should be specified rather than assumed.

On-site or off-site

On-site destruction means media never leaves under your custody in a readable state. It costs more, needs space and power, and slows the day. Off-site is cheaper and faster but introduces a transport leg during which the data still exists.

If transport is involved, the sealed-load procedure and the time between pickup and destruction are the two things worth specifying in writing. The other controls that make destruction secure are in what the word secure adds.

What a defensible certificate contains

• Serial numbers, device by device, not counts, not weights.
• The method applied to each device, and the standard referenced.
• Dates for each custody transfer, not just for the destruction.
• The operator and the facility where the work was performed.
• Exceptions: devices that failed erasure and what happened to them instead.

That last line is the one most often missing, and the one an auditor asks about first. The full list is on what a certificate of destruction has to contain.