# Byte-Level Binary Diffing with Rolling Hash Windows

## Module
BinaryIndex

## Status
IMPLEMENTED

## Description
Byte-level binary comparison using rolling hash windows that identifies exactly which byte ranges changed between binary versions. Produces binary proof snippets with section analysis and privacy controls to strip raw bytes. Supports stream and file-based comparison.

## Implementation Details
- **Modules**: `src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/`
- **Key Classes**:
  - `PatchDiffEngine` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/PatchDiffEngine.cs`) - core diffing engine computing byte-level differences between binary versions using function fingerprints
  - `FunctionDiffer` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/FunctionDiffer.cs`) - function-level comparison with semantic analysis option and call-graph edge diffing
  - `FunctionRenameDetector` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/FunctionRenameDetector.cs`) - detects function renames between versions using fingerprint similarity
  - `VerdictCalculator` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/VerdictCalculator.cs`) - computes patch verification verdicts from diff results
  - `InMemoryDiffResultStore` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/Storage/InMemoryDiffResultStore.cs`) - stores diff results with content-addressed IDs
- **Models**: `PatchDiffModels`, `DiffEvidenceModels`, `BinaryReference` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/Models/`)
- **Interfaces**: `IPatchDiffEngine`, `IDiffResultStore` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Diff/`)
- **Source**: SPRINT_20260112_200_004_CHGTRC_byte_diffing.md

## E2E Test Plan
- [ ] Submit two binary versions and verify byte-range differences are identified with correct offsets
- [ ] Verify section analysis identifies which ELF sections changed (.text, .data, .rodata)
- [ ] Verify privacy controls strip raw bytes from proof snippets when configured
- [ ] Verify `FunctionRenameDetector` correctly identifies renamed functions between versions
- [ ] Verify `VerdictCalculator` produces correct patch verification verdict (patched vs unpatched)
- [ ] Verify diff results are stored with deterministic content-addressed IDs