Griffinere Cipher 🔐

The Griffinere cipher is a custom encryption algorithm in C# designed for reversible, base64-normalized encryption using a repeating key. Inspired by the Vigenère cipher, it adds configurable alphabet support, input validation, and padding-based encryption length enforcement.

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📦 Installation

Clone this repository or copy the Griffinere.cs file into your .NET project.

https://github.com/RileyG00/Ciphers

In your code:

using Ciphers;

✨ Features

🔐 Encrypts and decrypts alphanumeric or custom alphabet-based strings

🧩 Allows defining your own alphabet

📏 Supports minimum-length encrypted responses via padding

✅ Includes strong validation for alphabet and key integrity

🧪 Unit tested with xUnit

🧰 Usage

1.1: Creating the Cipher Using the default alphabet:

string key = "YourSecureKey123";
Griffinere cipher = new(key);

Default alphabet includes:

A-Z
a-z
0-9

1.2: Creating the Cipher Using a custom alphabet:

string customAlphabet = "abcdef123456";
string key = "a1c";
Griffinere cipher = new(customAlphabet, key);

Alphabet Rules

1. Must not contain . (dot character)
2. All characters must be unique
3. All characters in the key must exist in the alphabet

2.1: Encrypt a String

string plainText = "Hello World 123";
string encrypted = cipher.EncryptString(plainText);

2.2: Encrypt a String with Minimum Length

string plainText = "Hello World 123";
string encrypted = cipher.EncryptString("Short text", minimumResponseLength: 24);

3.1: Decrypt a String

string decrypted = cipher.DecryptString(encrypted);
// Returns the original plain text

⚠️ Exceptions and Validations

Tables

Condition	Exception
Alphabet contains .	ArgumentException
Alphabet has duplicate characters	ArgumentException
Key contains characters not in alphabet	ArgumentException
Encrypting empty/null text	ArgumentNullException