Bit Rot

Overview

Bit rot describes undetected changes to stored bits from media defects, firmware bugs, cosmic rays, or file-system errors. Unlike film decay, digital corruption can be invisible until a decode fails—catastrophic when a single flipped bit breaks a frame header or checksum.

Causes and Vectors

Hard drives suffer from latent sector errors; optical and flash media degrade with age; file transfers without verification introduce mismatches. RAID protects against device failure but not all forms of silent corruption; backups that replicate bad bits are worthless.

Mitigation Strategy

• Checksums: Generate cryptographic hashes (MD5/SHA-256) at creation; verify on every move.
• Fixity Audits: Schedule periodic re-verification to detect drift.
• Redundancy: Keep geographically separate copies on different media types.
• Format Choice: Prefer simple, open, intra-frame image sequences (DPX/TIFF) over opaque monoliths for long-term.
• Write-Once Paths: Minimize ad-hoc edits to preservation masters; derive access copies separately.

Incident Response

When verification fails, isolate the bad copy, attempt sector-level recovery, and reconstitute from a known-good replica. Maintain chain-of-custody logs so courts, studios, and insurers trust the master’s provenance.

Related Terms

• MD5 checksum, LTO tape, digital preservation master, fixity.