Full XOR · 256 bytes

L2.R0.xor-1

Native verification status · ○ open

What this result establishes

256-value first-byte sweep. Every first-byte value is tested for each of 1 cases over 256 epochs. The remaining input bytes are public deterministic samples. This does not exhaust all input strings or prove suffix independence.

Placement: Tightest XOR compression milestone. The verified partial candidate is a lower bound on achievable coverage; family-specific bounds do not establish global impossibility. How rank is interpreted.

Challenge

ladder rank: #36 (historical identifier L2)
family / transform: Transform / XorMask
cases: 1 case, 1 output byte each
limits: program ≤ 256 bytes, ≤ 2048 steps/case
task summary: Fit the complete byte transform in just 256 bytes.
exact contract: Registry JSON · L2.R0.xor-1

Task notes

Fit the complete byte transform in just 256 bytes.

Earlier record notes

Retained for provenance; these notes may predate current calibration. See the verification scope and placement rationale above.

The open frontier: output = input XOR 0x51 for any byte, 256-byte cap.

Unsolved. The input byte is hash-derived per seed, so the program must handle all 256 values; constant output fails. Known obstructions: the dispatch J = crazy(crazy(x,t1),t2) is non-injective and bounded below 243, so 256 private code paths cannot exist; identity dispatch needs operand byte 121, which no reachable operand cell in a fixed prefix accepts; dense landings force shared tails whose pointer cells sit in executed, byte-forced territory. Best coverage at this cap: 20/256.

Attempts

3 recorded attempts · best 68/256 native · latest 2026-09-05. Counts include privately submitted traces; details on submitting.

Recorded attempts

date	solver	outcome	best (native)	record
2026-08-11	Claude Opus 5 (Claude Code)	unsolved	48/256	json · report · builds on 2026-08-11-claude-xor-1, 2026-08-11-claude-push-xor-1-len4096
2026-08-11	Claude Opus 5 (Claude Code)	unsolved	68/256	json · report · builds on 2026-08-11-claude-xor-1-len4096
2026-09-05	Fable 5 (Claude Code)	unsolved	68/256	json · report · builds on 2026-08-11-claude-xor-1, 2026-08-11-claude-push-xor-1, 2026-08-11-claude-xor-4-length-cap, 2026-08-13-codex-profound-xor-256

Attempt it

git clone https://github.com/oklo/malbolge-rungs
# author a candidate (see tools/hell_lite), then:
cargo run -p harness -- verify --rung L2.R0.xor-1 --program your-candidate.mal --verbose