Used by some professional shops (Flylogic uses both it and wet etching). Procedure

• Apply very fine abrasive (optical polishing compound, <100nm grit is ideal) to turntable of some sort
• Gently press die against turntable, checking periodically if layer is fully removed

Advantages

• Safe
• Very flat surface
• Moderate cost

Disadvantages

• Requires precision abrasives which may be expensive
• Labor intensive

Procedure

• Secure (glue) die to surface
• Use fine sandpaper (1200+?) to remove a layer
• Using polishing paste, Dremel polish layer to photographic quality

Advantages

• Materials readily available
• Safe (for user)
• Low cost

Disadvantages

• May not be as repeatable as chemical etching
• Labor intensive
• Risky, easy to grind too far

Notes

• Nohl used Dremel + sandpaper for his MiFare Classic attacks according to CCC talk