How to Encrypt a File in C# and Decrypt it (2024)

How to Encrypt a File in C# and Decrypt it

Encrypting a file in C# involves using cryptographic algorithms to convert the file’s contents into an unreadable format that can only be deciphered with the appropriate decryption key. Here’s a basic example of how to encrypt a file in C# using the AesManaged class, which is a symmetric encryption algorithm:

using System;
using System.IO;
using System.Security.Cryptography;

using (FileStream inputFileStream = new FileStream(inputFile, FileMode.Open))
using (FileStream outputFileStream = new FileStream(outputFile, FileMode.Create))
using (CryptoStream cryptoStream = new CryptoStream(outputFileStream, encryptor, CryptoStreamMode.Write))
{
int data;
while ((data = inputFileStream.ReadByte()) != -1)
{
cryptoStream.WriteByte((byte)data);
}
}
}
}

public static void Main(string[] args)
{
string inputFile = “input.txt”;
string outputFile = “encrypted.bin”;
string password = “YourSuperSecretPassword”;

EncryptFile(inputFile, outputFile, password);

Console.WriteLine(“File encrypted successfully.”);
}
}

In this example:

1. We use the AesManaged class for symmetric encryption. It’s essential to derive encryption keys and IV from a password, and you should use a strong password.

1. We create an encryptor using the derived key and IV.
2. We open the input and output file streams and use a CryptoStream to encrypt the data from the input file and write it to the output file.
3. Make sure to replace "input.txt", "encrypted.bin", and "YourSuperSecretPassword" with your actual file paths and password.

Remember to handle exceptions and use secure key management practices when implementing encryption in a real application. Additionally, consider using other encryption methods, such as RSA for asymmetric encryption, depending on your specific use case and security requirements.