MicroCrypt

MicroCrypt – For The Ones We Hold Dear

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 4 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 4 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 76 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 for valuable feedback, and to Ffna Sol for the MicroCrypt icon design.

A big thank you also goes to the following people who localized MicroCrypt:

Uncle Lem – Russian edition