NIST SP 800-88 Rev 2 3.1.2: Purge: physical or logical techniques that defeat laboratory recovery while keeping the ISM reusable; prefer purge to clear; choose techniques from IEEE 2883; cryptographic erase may be the only purge option for virtual storage; degauss only magnetic media with a matched degausser

What does 3.1.2 require?

The purge method makes recovery of the target data infeasible even with state-of-the-art laboratory techniques while leaving the ISM potentially reusable; it is never appropriate for hard copy, and where possible it is used in preference to clear. Logical purge techniques vary by media type and are chosen from IEEE 2883: overwrite, block erase and cryptographic erase through dedicated, standardised sanitize commands that bypass the abstraction of ordinary read and write commands. Cryptographic erase is fast but depends on the pedigree of the cryptography and on preconditions set out in Section 3.2. For virtual or logical storage such as cloud storage it may be the only viable purge option, so organisations understand their purge options and their effectiveness before storing sensitive data there. Degaussing is a physical purge technique for magnetic tape and disks only, never for flash; many degaussers lack the force for modern high-coercivity and hybrid media, degaussing can disable a device without sanitizing it, and it is not an approved destroy technique, so IEEE 2883 or NSA/CSS Policy Manual 9-12 are consulted.