Copy Protection

Overview

Publishers wanted to sell software. Users wanted to copy it. Copy protection became an arms race — each new technique defeated, each defeat spawning new protection. From bad sectors to code wheels to manual lookups to hardware dongles, the battle between protection and cracking shaped software distribution and spawned the demoscene’s “crack intro” art form.

Disk-based protection

Disk protections work by writing data the standard format spec doesn’t allow — the original drive can read it, but a normal copy program can’t write it back.

Method	Technique	How it defeats copying
Bad sectors	Intentional CRC-error sectors at known locations	Standard copiers refuse to write CRC-bad sectors
Non-standard formatting	Tracks with extra/missing/oversized sectors	Standard format-and-copy ignores the unusual layout
Weak bits / fuzzy bits	Bits that read inconsistently every time	A “good” copy is consistent, which is itself a tell
Spiral tracks	Track that drifts radially across the disk	Drives can’t reliably step across track boundaries
Half-tracks	Data between the standard track positions	Most consumer drives can’t write to half-tracks
Long tracks	Sectors larger than the format spec allows	Copy software truncates them
Density variations	Different bit-cell timings on different tracks	Standard formats use uniform timing
Sync-mark detection	Custom sync patterns the protection looks for	Recopied tracks have different sync-mark layout

Tape-based protection

Method	Technique
Speedlock-style turbo + checksum	Custom turbo loader bundled with verification of pulse pattern
Header puzzles	Multiple header blocks, decoder routine reassembles them
Anti-tape-deck-recording	Pulses too fast for consumer cassette decks to faithfully copy

Tape protection is necessarily weaker than disk because audio is a continuous medium — you can always record the analogue signal and replay it. The defence was usually time-cost: copying took as long as the original load.

Manual-based protection

Type	Implementation	Examples
Code wheels	Rotating cardboard decoder	Monkey Island (Dial-a-Pirate), Pool of Radiance
Word lookup	“Word 3, line 5, page 12 of the manual”	Zak McKracken, Indiana Jones and the Last Crusade
Symbol matching	Match a screen image to a manual page	Wing Commander, Ultima series
Dark-text print	Manual printed in red-on-red ink	Hard to photocopy in mono; often paired with red-cellophane decoder
Trivia / age-gates	“What is the capital of …?” pulled from manual	Leisure Suit Larry age-verification, Where in the World Is Carmen Sandiego?

See Manual Protection for the broader picture.

Lenslok

Aspect	Detail
System	A small plastic prism that distorts a stretched on-screen image into legible text
Use	Hold to TV, decode 2-letter code, type into game
Notable failures	Image scaling differs by TV size; small TVs left it impossible; lens easily lost
Reception	Universally hated

See Lenslok for the standalone story.

Hardware dongles

Platform	Application
Amiga / Atari ST	Parallel-port dongles for high-end software (CAD, music)
PC	Professional software (AutoCAD, Pro/E, music) into the 2000s
Arcade	“Security chips” embedded in JAMMA boards (Capcom CPS-2 SEGA System 32)
PlayStation 1	Mod-chips and disc-based protections worked the other direction

Dongles eventually evolved into USB security keys (HASP, SafeNet, Sentinel) used by enterprise software through the 2010s.

Notable protection systems

System	Platform	Notes
Copylock (Rob Northen)	Amiga, Atari ST	The dominant 16-bit disk protection; see Copylock
Speedlock (Rob Northen)	ZX Spectrum	Tape-based turbo + protection; same designer as Copylock
Rapidlok	C64	Disk protection bundled with fastloader; common late-80s commercial titles
Macrovision	PlayStation, PS2	Optical-disc subchannel data
SecuROM	PC	Late 90s / 2000s; CD/DVD-based, became infamous for system instability
StarForce	PC	Aggressive 2000s-era driver-level protection
SafeDisc	PC	Microsoft-owned CD protection

Cracker techniques

Method	What it does	Counter from publishers
Disk image analysis	Capture every track’s raw data, find what’s unusual	Move check to encrypted code
Static patching	Find the protection check, NOP it out	Multiple checks, scattered throughout the program
Trainers	Bypass with options menus or cheats	Anti-debug, integrity self-checks
Complete rewrite	Replace the whole loader with a fresh one	Encrypt the actual game code with the protection key

The result was a years-long escalation: by the late 1990s most commercial games had layered protections that could only be defeated by reverse-engineering the entire protection runtime.

User impact

Problem	Effect
Backup inability	Can’t make personal copies; original disk wears out
Hardware failures	Floppy drive dies, game dies with it
False positives	Legitimate copies rejected on slightly out-of-spec drives
Load times	Extended by checks (every load runs the protection too)
Lost manuals	Whole game becomes unplayable
Lost dongles	Same

These frustrations drove legitimate users to seek out cracked versions — protection that punishes paying customers is the textbook anti-pattern that the industry took decades to admit.

Legacy

Era technique	Modern equivalent
Disk bit-pattern protections	DRM, online activation servers
Manual lookups	Account systems (Steam, Epic, console accounts)
Hardware dongles	USB security keys, hardware-backed attestation
Crack intro culture	Demoscene endured; the technical skills informed early indie / homebrew
Arms race	Continues today, only the medium changes

The anti-piracy arms race