Schneier, Gutmann, and Random Overwrite Profiles

Applies to: All editions

Bruce Schneier’s Algorithm

This profile uses seven passes:

  1. 0x00;
  2. 0xFF;
  3. cryptographically generated random data.
  4. cryptographically generated random data.
  5. cryptographically generated random data.
  6. cryptographically generated random data.
  7. cryptographically generated random data.

Peter Gutmann’s Algorithm

This profile uses 35 passes consisting of:

  • four initial random passes;
  • twenty-seven fixed-pattern passes;
  • four final random passes.

The profile can require a very long execution period on modern high-capacity devices. It should be selected only where an approved procedure explicitly requires it.

Random Byte Overwrite — 3 pass

This profile writes three independent cryptographically generated random passes across the addressable logical range.

Aperiodic Random Overwrite

This profile writes two cryptographically generated random passes.

Verification limitation

These profiles finish with random data. DriveErase does not retain the entire random stream needed to perform a later sampled comparison against the exact final bytes. A completed result therefore records successful writes and other execution evidence but does not claim fixed-final-pattern verification.

Selection guidance

Random and high-pass profiles do not automatically provide stronger practical assurance than a correctly selected, completely executed, verified modern method.

Always consider:

  • The device technology;
  • The ability to cover the relevant storage scope;
  • Media errors;
  • Firmware sanitization availability;
  • Verification requirements;
  • Maintenance duration;
  • Device wear;
  • The approved organizational standard.

On flash storage, repeated host writes still do not prove that hidden, remapped, or retired physical cells were processed.