1. Hard Disk Drive (HDD)#

• Principle: Data is stored on magnetic tracks of spinning platters and read/written via magnetic heads.
• Sanitization Challenges: Conventional deletion operations (e.g., OS file deletion) only remove file system metadata (like FAT tables or MFT records); the actual data remains on the tracks. Achieving irreversible erasure requires methods such as multiple-pass overwriting, degaussing, or physical destruction.
• Recommended Methods: Multiple-pass overwriting, Degaussing, Physical shredding.

2. Solid State Drive (SSD) / NVMe Drive#

• Principle: Data is stored in NAND flash cells and managed by a controller using FTL (Flash Translation Layer) for read/write operations and wear leveling.

• Sanitization Challenges:

  • FTL Interference: Traditional overwriting is inefficient on SSDs. The FTL maps overwrite operations to new empty blocks, leaving original data blocks marked as “invalid” but not immediately erased until Garbage Collection occurs. This leads to data remanence.

  • Lifetime Degradation: Flash cells have finite P/E (Program/Erase) Cycles. Excessive overwriting significantly shortens the SSD’s lifespan.

• Recommended Methods: Controller-based Secure Erase (SE) or Sanitize commands (e.g., ATA/NVMe standards). These reset all cells (including over-provisioned space) to factory defaults via internal discharge, ensuring data is unrecoverable with minimal wear. Physical destruction is also highly reliable.

1. OnePass (Single Pass)#

A single full-disk write of a fixed pattern (e.g., 0x00, 0xFF) or random data.

• Pros: Fast.
• Security: Low.
• Use Case: Non-sensitive data requiring rapid clearance.

2. GA/T 1143-2014 (China)#

Technical requirements for data destruction software products.

• Single Pass: Same as OnePass.
• 3-Pass Method: 1st pass: Fixed character (e.g., 0x00); 2nd pass: Complement (e.g., 0xFF); 3rd pass: Random characters.
• 7-Pass Method: Alternates between fixed characters, complements, single-character patterns, and random characters across seven cycles.
• Use Case: High-sensitivity data where maximum unrecoverability is required.

3. DoD 5220.22-M (USA)#

The U.S. Department of Defense standard upon which most global standards are derived.

• Short (3-Pass): 0x00, 0xFF, Random.
• Standard (ECE/7-Pass): A more rigorous sequence including multiple passes of 0x00, 0xFF, and random data.
• Security: Extremely high; designed to overcome the magnetic remanence effect.

4. IEEE Std 2883-2022#

Requires at least two passes: Fixed character followed by its complement, with a verification step involving a random sampling of ≥5% of the addressable space.

Crucial Note: Multiple-pass standards (DoD, GA/T) are designed specifically for the physical characteristics of HDDs. They are not recommended for SSDs/NVMe drives due to FTL mechanisms, wear issues, and inefficiency compared to Secure Erase commands.

NIST SP 800-88 Purge / Secure Erase (SE)#

• Principle: Sends specific instructions (e.g., NVMe Format NVM with Sanitize) to the controller. The controller resets the voltage levels of all NAND cells (including over-provisioned areas), returning the drive to its factory “out-of-box” state.
• Advantages: - Thorough: Clears all physical blocks, including those hidden from the OS.
  • Fast: Significantly faster than multi-pass overwriting.
  • Low Wear: Minimal impact on P/E cycles.
• Requirements: Requires hardware/firmware support. BIOS/UEFI or drive passwords must be disabled before execution.