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Simple Symmetric File Encryption

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The following code sample demonstrates a quick and easy means of encrypting and decrypting files using the AES symmetric encryption algorithm.

The code randomly generates the Salt and Initialization Vectors each time a file is encrypted, meaning that encrypting the same file with the same password will always lead to different output. The salt and IV are written to the output file so that only the password is required to decrypt it. 

public static void ProcessFile(string inputPath, string password, bool encryptMode, string outputPath)
{
    using (var cypher = new AesManaged())
    using (var fsIn = new FileStream(inputPath, FileMode.Open))
    using (var fsOut = new FileStream(outputPath, FileMode.Create))
    {
        const int saltLength = 256;
        var salt = new byte[saltLength];
        var iv = new byte[cypher.BlockSize / 8];

        if (encryptMode)
        {
            // Generate random salt and IV, then write them to file
            using (var rng = new RNGCryptoServiceProvider())
            {
                rng.GetBytes(salt);
                rng.GetBytes(iv);
            }
            fsOut.Write(salt, 0, salt.Length);
            fsOut.Write(iv, 0, iv.Length);
        }
        else
        {
            // Read the salt and IV from the file
            fsIn.Read(salt, 0, saltLength);
            fsIn.Read(iv, 0, iv.Length);
        }

        // Generate a secure password, based on the password and salt provided
        var pdb = new Rfc2898DeriveBytes(password, salt);
        var key = pdb.GetBytes(cypher.KeySize / 8);

        // Encrypt or decrypt the file
        using (var cryptoTransform = encryptMode
            ? cypher.CreateEncryptor(key, iv)
            : cypher.CreateDecryptor(key, iv))
        using (var cs = new CryptoStream(fsOut, cryptoTransform, CryptoStreamMode.Write))
        {
            fsIn.CopyTo(cs);
        }
    }
}
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Cryptography:
* Modern Examples of Symmetric Authenticated Encryption of a string
* Introduction to Symmetric and Asymmetric Encryption
* Password Hashing
* Simple Symmetric File Encryption
* Cryptographically Secure Random Data
* Fast Asymmetric File Encryption
Table Of Contents
0 Getting Started With C#
1 Literals
2 Operators
3 Conditional Statements
4 Equality Operator
5 Equals and GetHashCode
6 Null-Coalescing Operator
7 Null-Conditional Operators
8 nameof Operator
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96 Networking
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110 Async/Await, BackgroundWorker, Task and Thread examples
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118 Task Parallel Library TPL Dataflow Constructs
119 Functional Programming
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124 IComparable
125 Accessing Databases
126 Using SQLite
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130 Structural Design Patterns
131 Creational Design Patterns
132 Implementing Decorating Design Pattern
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134 System.Management.Automation
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137 Simulating C Unions with C# Structs
138 Reactive Extensions Rx
139 AsseblyInfo.cs examples
140 Creating Console Application
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142 ObservableCollection
143 Hash Functions
144 Generating Random Numbers
145 Cryptography
146 Unsafe Code in .NET
147 C# Script
148 Runtime Compile
149 Interoperability
150 .NET Compiler Platform Roslyn
151 Creating Own MessageBox in Windows Form Application
152 Including Font Resources
153 Garbage Collector
154 Windows Communication Foundation
155 Contributors