MicroCrypt

MicroCrypt is a small, cross-platform symmetric encryption tool for
desktop and mobile devices. It focuses on simplicity, portability,
and modern cryptographic defaults while avoiding unnecessary metadata
in encrypted output.

Security Considerations

• Memory Safety: MicroCrypt uses memguard to securely store
  sensitive data in locked memory, preventing it from being swapped
  to disk or appearing in core dumps.
• Clipboard Handling: Copied text is automatically cleared from
  the clipboard after 15 seconds to prevent data leakage.
• Auto-Clear: The application automatically wipes all sensitive
  data after 5 minutes of inactivity.
• Rate Limiting: Failed decryption attempts are limited to 5 per
  minute to prevent brute-force attacks.

Features

• Symmetric file encryption using AES-256-GCM
• Password-based key derivation using Argon2id (OWASP-recommended parameters)
• ISO/IEC_7816-4 in 1 KB block multiples
• Minimum 15-character password requirement (NIST 800-63B compliant)
• Simple graphical interface built with the Fyne toolkit
• Works on Linux, macOS, Windows, Android and iOS
• Automatic memory cleanup on inactivity
• Dark/light theme toggle

Cryptography Overview

MicroCrypt uses the following components:

1. AES-256-GCM
   Provides authenticated encryption, ensuring both confidentiality and
   integrity of the encrypted data.

2. Argon2id A memory-hard password-based key derivation function designed to
   resist brute-force and GPU-based attacks. Parameters:

   • Time: 3 passes
   • Memory: 64 MB
   • Parallelism: 4 threads

3. ISO/IEC 7816-4 Padding Data is padded to 1 KB boundaries before encryption.
   This helps reduce leakage about the original file size.

Encrypted Output Format

MicroCrypt produces a self-contained base64-encoded string containing:

Component	Length	Purpose
Salt	16 bytes	Prevents rainbow table attacks
Nonce	12 bytes	Ensures unique ciphertext per encryption
Ciphertext	Variable	AES-256-GCM encrypted data

The three components are concatenated and base64-encoded with line breaks
every 24 characters for easier handling.

Use Cases

MicroCrypt is suitable for:

• Encrypting private messages or notes with a simple GUI
• Cross-platform workflows where the same tool is needed on desktop and
  Android or iOS
• Users who want strong encryption without complex configuration
• Situations where avoiding metadata leakage is important

MicroCrypt is not intended for:

• For input of large messages or pasting files
• Public-key encryption or key exchange Workflows
• Enterprise or multi-user key Management
• Automated or scripted encryption Pipelines

Special thanks go to Maria Sophia and Arno Welzel for their valuable feedback, and to Ffna Sol for the MicroCrypt icon design.

If you like MicroCrypt, as much as I do, consider a small
donation in crypto currencies or buy me a coffee.

BTC: bc1qkluy2kj8ay64jjsk0wrfynp8gvjwet9926rdel    
Nym: n1f0r6zzu5hgh4rprk2v2gqcyr0f5fr84zv69d3x     
XMR: 45TJx8ZHngM4GuNfYxRw7R7vRyFgfMVp862JqycMrPmyfTfJAYcQGEzT27wL1z5RG1b5XfRPJk97KeZr1svK8qES2z1uZrS      

MicroCrypt is dedicated to Alice and Bob.