ENDY 1.0 - Encryption Utility

ENDY 1.0 is a C++ command-line utility designed to demonstrate the fundamental architecture of a symmetric encryption system. It implements a complete cryptographic pipeline including salt generation, password-based key derivation (PBKDF2-inspired), XOR stream encryption, and message integrity verification (MAC).

This project is strictly for educational purposes to illustrate cryptographic concepts without relying on external libraries such as OpenSSL.

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Example Usage

The following screenshots show a sample testcase for both Encryption and Decryption:

Proper encryption and decryption:

Using wrong password for decryption:

Tampering encrypted text to interfere with MAC hence losing integrity and failing:

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System Architecture

The following diagrams illustrate the data flow for the encryption and decryption processes, detailing how the password and salt are transformed into the final encrypted payload and reversed.

Encryption:

Decryption:

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Encrypted Payload Structure

The output format is a Fixed-Width string containing all metadata required for decryption. It does not use delimiters; instead, it relies on strict character counts for parsing.

classDiagram
    class Payload {
        +String Version (5 chars)
        +Hex Salt (32 chars)
        +Hex Iterations (8 chars)
        +Hex MAC (16 chars)
        +Hex Ciphertext (Variable)
    }

    note for Payload "Format: [VERSION][SALT][ITERATIONS][MAC][CIPHERTEXT]"

Loading

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Payload Fields

Component	Length(Chars)	Type	Description
Version	5	String	Protocol identifier fixed as "ENDY1"
Salt	32	Hex String	16 bytes of random entropy (hex encoded)
Iterations	8	Hex String	Key derivation work factor (padded hex)
MAC	16	Hex String	64-bit Integrity signature (truncated hash)
Ciphertext	Variable	Hex String	Encrypted message data (rest of string)

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Features

• Zero Dependencies: Uses only the C++17 standard library.
• Fixed-Width Protocol: Clean, professional output format without delimiters.
• Unique Salting: Random std::random_device salt per encryption.
• Key Stretching: Iterative hashing to resist brute-force attacks.
• Integrity Verification: Encrypt-then-MAC ensures tamper resistance.
• Versioned output format for forward compatibility

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Getting Started

Prerequisites

• C++ compiler supporting C++17
• Optional build tools such as Make

Compilation

g++ -std=c++17 -o endy endy.cpp

Usage

./endy

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Example

Encrypted output example:

ENDY18fb959ea0198df83f5f92ba95187b3c90000271000000000a59860aaf4fc565c4dc17cfa6c92f901

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Technical Implementation Details

Key Derivation Function

The password is never used directly as an encryption key.

Input:

• User password
• Random salt

Process:

• Password and salt are hashed 10000 times using std::hash
• The final hash seeds std::mt19937 to generate a deterministic key stream

Output:

• Key stream matching the plaintext length

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Stream Cipher XOR

Encryption: Ciphertext[i] = [ Plaintext[i] ] XOR [ Key[i] ]

Decryption: Plaintext[i] = [ ciphertext[i] ] XOR [ Key[i] ]

The same operation is used for encryption and decryption.

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Integrity Check MAC

A message authentication code is generated after encryption.

Formula: MAC = Hash(Ciphertext concatenated with DerivedKey)

During decryption, the MAC is recomputed. If the values do not match, decryption is aborted immediately.

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Disclaimer

This software uses std::hash and std::mt19937 which are not cryptographically secure primitives. It is intended strictly for educational use and must not be used to protect sensitive data.