# PFES-ENG-021 — Media Identity

**Status:** Active  
**Knowledge Cycle Stages:** Identify

## Purpose

Establish the engineering identity of optical media and its acquired representations.

## Engineering Problem

Filenames and hashes cannot describe all physical, logical, security, and provenance characteristics.

## Historical Engineering Evolution

Identity expanded from title and checksum to disc IDs, media family, topology, authentication resources, filesystem, mastering data, and acquisition context.

## Engineering Discoveries

- Hashes identify known artifacts but do not fully define media identity.
- Identity grows with engineering knowledge.

## Architectural Decisions

- Preserve observed identity separately from inferred identity.
- Link identity to acquisition and validation evidence.

## Knowledge Produced

- Media identity records
- Lookup keys
- Validation references

## Knowledge Consumed

- Images
- Sidecars
- Hashes
- Descriptors
- Provenance

## Current Engineering State

Current identity may include title identifiers, media family, partition layout, filesystem, authentication resources, PFI, DMI, security data, and cryptographic hashes.

## Engineering Lessons

- A hash library is useful for known media but cannot replace structural identity.

## Negative Knowledge

Project Frankenstein no longer assumes:

- Filename equals identity.
- Filesystem identity equals disc identity.

## Current Implementations

- Sidecar metadata
- Redump comparison
- Disc-specific reports

## Future Implementations

- Canonical media identity database
- Automatic recognition

## Open Questions

To be expanded during engineering review.

## Why This Chapter Exists

Media comparison and validation require precise identity.
