HashOwl

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Do you often worry that the precious files on your hard drive have been corrupted by cosmic rays? If so, HashOwl is an excellent tool for detecting that.

HashOwl is a high-performance, multithreaded command-line tool written in modern C++. It calculates hashes for files or whole directories, can export a JSON snapshot, and can later verify a target against that snapshot.

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Key Features

• Fast multithreaded scanning for directories.
• Supports both single-file and directory-tree hashing.
• Generates structured JSON snapshots for later integrity checks.
• Verification mode reports:
  • passed files
  • modified files
  • missing files
  • untracked files
• Built-in progress display with throughput (MB/s or GB/s).

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Supported Algorithms

• crc32 (default)
• crc64
• md5
• sha1
• sha256
• sha384
• sha512
• blake3

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Build Requirements

Current tested setup:

• OS: Windows
• Compiler: MSVC
• Build system: CMake + Ninja presets
• CMake version: 3.21+

Third-party dependencies include nlohmann/json, indicators, blake3, and libdeflate.

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Build

Use the CMake presets in this repository:

cmake --preset x64-debug
cmake --build out/build/x64-debug

cmake --preset x64-release
cmake --build out/build/x64-release

Additional presets are available in CMakePresets.json (for example x86-debug and x86-release).

Build Notes

• The project is currently Windows-focused.
• MD5 and SHA-family hashing use native bcrypt.lib.
• Release presets enable aggressive MSVC optimization flags.

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Usage

./out/build/x64-release/src/HashOwl.exe <path> [--algo <md5|sha1|sha256|sha384|sha512|crc32|crc64|blake3>] [-o [output_path]] [--verify <snapshot.json>]

Options

• --algo <algorithm>: Select hashing algorithm (default: CRC32).
• -o [output_path]: Export snapshot JSON.
  • If only -o is provided, output defaults to <target_name>_hashowl.json next to the target.
  • If output_path is a directory, the default file name is created under that directory.
  • If output_path is a file path, that exact path is used.
• --verify <snapshot.json> / -v <snapshot.json>: Verify target against a previous snapshot.
• --help / -h: Print help.

Exit Codes

• 0: Success
• 1: Argument error
• 2: Runtime error
• 3: Verification failed (modified or missing files)

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Examples

1) Hash a single file (default algorithm)

./out/build/x64-release/src/HashOwl.exe C:\path\to\file.txt

2) Hash a directory with SHA512

./out/build/x64-release/src/HashOwl.exe C:\path\to\folder --algo SHA512

3) Hash and export JSON with default output name

./out/build/x64-release/src/HashOwl.exe C:\path\to\folder -o

4) Export JSON to a specific path

./out/build/x64-release/src/HashOwl.exe C:\path\to\folder -o C:\custom\output\snapshot.json

5) Verify target against a snapshot

./out/build/x64-release/src/HashOwl.exe C:\path\to\folder --verify C:\path\to\folder_hashowl.json

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Verification Output (Example)

Verification Report:
------------------------------------------------
Passed:    1042 files
Modified:  2 files
   - config\settings.ini
   - data\pagefile.sys [READ ERROR]
Missing:   1 files
   - docs\old_readme.md
Untracked: 5 files
   - temp\new_cache.tmp
------------------------------------------------
Total Time: 0.45 seconds