File signatures, also known as magic numbers, are unique sets of bytes at the beginning of files that help in identifying the file type regardless of the file’s extension. Validating a file’s signature is crucial for security and data integrity, especially in environments where file content should match its extension.

Here’s a list of some common file signatures with their corresponding extensions, followed by a C# example of how to validate a file’s signature based on its expected type:

Common File Signatures

1. JPEG Image: .jpeg, .jpg – FF D8 FF
2. PNG Image: .png – 89 50 4E 47 0D 0A 1A 0A
3. GIF Image: .gif – 47 49 46 38
4. TIFF Image: .tiff – 49 49 2A 00 or 4D 4D 00 2A
5. BMP Image: .bmp – 42 4D
6. PDF Document: .pdf – 25 50 44 46
7. ZIP Archive: .zip – 50 4B 03 04 or 50 4B 05 06 or 50 4B 07 08
8. RAR Archive: .rar – 52 61 72 21 1A 07 00
9. 7z Archive: .7z – 37 7A BC AF 27 1C
10. MS Office/OpenOffice Documents: .docx, .xlsx, .pptx – 50 4B 03 04
11. MS Office 97-2003 Document: .doc, .xls, .ppt – D0 CF 11 E0 A1 B1 1A E1
12. WAV Audio: .wav – 52 49 46 46
13. AVI Video: .avi – 52 49 46 46
14. MP3 Audio: .mp3 – FF FB or 49 44 33
15. FLV Video: .flv – 46 4C 56 01
16. Real Audio: .ram – 2E 72 61 FD
17. Real Media: .rm – 2E 52 4D 46
18. MPEG Video: .mpeg, .mpg – 00 00 01 BA or 47 40
19. QuickTime Video: .mov – 00 00 00 14 66 74 79 70
20. MIDI Audio: .midi – 4D 54 68 64
21. ISO Image: .iso – 43 44 30 30 31
22. Executable File: .exe – 4D 5A
23. ELF Executable: .elf – 7F 45 4C 46
24. VMDK File: .vmdk – 4B 44 4D
25. AIFF Audio: .aiff – 46 4F 52 4D 00
26. XML Document: .xml – 3C 3F 78 6D 6C 20
27. SQLite Database: .sqlite – 53 51 4C 69
28. Photoshop Document: .psd – 38 42 50 53
29. MP4 Video: .mp4 – 00 00 00 18 66 74 79 70
30. AutoCAD Drawing: .dwg – 41 43 31 30

C# Code to Validate File Signature

The following C# function checks the file signature by comparing the beginning bytes of the file to known signatures:

using System;
using System.Collections.Generic;
using System.IO;

public class FileSignatureValidation
{
    private static Dictionary<string, List<byte[]>> fileSignatures = new Dictionary<string, List<byte[]>> {
        { ".jpeg", new List<byte[]> { new byte[] { 0xFF, 0xD8, 0xFF } } },
        { ".png", new List<byte[]> { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A } } },
        // Add more signatures here
    };

    public static bool ValidateFileSignature(string filePath)
    {
        using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            using (BinaryReader br = new BinaryReader(fs))
            {
                var fileExt

 = Path.GetExtension(filePath).ToLowerInvariant();
                if (fileSignatures.ContainsKey(fileExt))
                {
                    var headerBytes = br.ReadBytes(fileSignatures[fileExt][0].Length);
                    foreach (var sig in fileSignatures[fileExt])
                    {
                        if (headerBytes.SequenceEqual(sig))
                        {
                            return true;
                        }
                    }
                }
                return false;
            }
        }
    }

    public static void Main(string[] args)
    {
        var filePath = @"path\to\your\file.jpg";
        bool isValid = ValidateFileSignature(filePath);
        Console.WriteLine($"File signature validation: {isValid}");
    }
}

This code initializes a dictionary with file signatures and checks if the beginning bytes of a file match any of the expected signatures for that file extension. You would need to expand the fileSignatures dictionary to include more file types and their corresponding signatures.