SimpleCrypt v1.5

A multi-algorithm file encryption tool built in Rust with a cross-platform GUI.

SimpleCrypt encrypts and decrypts files using modern authenticated encryption algorithms. It runs on macOS, Windows, and Linux as both a command-line tool and a native desktop application.

Features

• 4 encryption algorithms — choose the right balance of speed and security
• Cross-platform GUI — native desktop app built with Tauri v2 and Svelte
• Command-line interface — scriptable CLI with clap for automation and power users
• Configurable defaults — TOML config file for algorithm, theme, and behavior preferences
• Backward compatible — decrypts files created by SimpleCrypt v1.x
• Secure by design — PBKDF2 key derivation, memory zeroization, constant-time comparisons, atomic file writes

Supported Algorithms

Algorithm	Type	Best For
AES-256-GCM (default)	AEAD	General use, hardware-accelerated on modern CPUs
AES-256-CBC	HMAC-SHA256	Legacy compatibility with v1.x files
ChaCha20-Poly1305	AEAD	Devices without AES hardware instructions
XChaCha20-Poly1305	AEAD	Maximum nonce safety (24-byte nonce)

All algorithms use PBKDF2-SHA256 for key derivation with adaptive iteration counts based on file size (10,000–600,000 iterations).

Project Structure

SimpleCrypt/
Cargo.toml # Workspace root
simplecrypt-core/ # Shared encryption library
simplecrypt-cli/ # Command-line interface
simplecrypt-gui/ # Tauri v2 desktop application

Prerequisites

• Rust (1.70+)
• Node.js (18+) — for the GUI frontend only
• OpenSSL development libraries (for AES-256-CBC legacy support)

Platform-specific dependencies

macOS:

brew install openssl

Ubuntu/Debian:

sudo apt install libssl-dev libwebkit2gtk-4.1-dev libappindicator3-dev librsvg2-dev

Windows:

Install OpenSSL via vcpkg or download prebuilt binaries. Tauri requires WebView2 (included in Windows 10/11).

Building

Build everything

cargo build --workspace

Build only the CLI

cargo build -p simplecrypt-cli

Build only the GUI

cd simplecrypt-gui/frontend && npm install &&cd ../..
cargo build -p simplecrypt-gui

Build for release

cargo build --workspace --release

The release binary is at target/release/simplecrypt.

Usage — Command Line

Encrypt a file

# Uses default algorithm (AES-256-GCM) — prompts for password
simplecrypt encrypt myfile.txt
# Specify algorithm and password inline
simplecrypt encrypt myfile.txt "mypassword" --algorithm chacha20-poly1305
# Create a backup before overwriting
simplecrypt encrypt myfile.txt --backup

Decrypt a file

# Auto-detects algorithm from the encrypted file
simplecrypt decrypt myfile.txt
# With password inline
simplecrypt decrypt myfile.txt "mypassword"

Encrypt/decrypt a directory

simplecrypt encrypt-dir ./documents "mypassword" --algorithm aes-256-gcm
simplecrypt decrypt-dir ./documents "mypassword"

Preview without changes

simplecrypt encrypt myfile.txt --dry-run

List available algorithms

simplecrypt algorithms

Output:

Available encryption algorithms:
aes-256-cbc AES-256-CBC (Legacy) (key: 32B, nonce: 16B, requires HMAC)
aes-256-gcm AES-256-GCM (key: 32B, nonce: 12B, AEAD)
chacha20-poly1305 ChaCha20-Poly1305 (key: 32B, nonce: 12B, AEAD)
xchacha20-poly1305 XChaCha20-Poly1305 (key: 32B, nonce: 24B, AEAD)

View or change configuration

# Show current config
simplecrypt config --show
# Change default algorithm
simplecrypt config --set encryption.algorithm=chacha20-poly1305
# Enable auto-backup
simplecrypt config --set security.backup_on_encrypt=true
# Change theme
simplecrypt config --set ui.theme=dark

Usage — GUI

Run in development mode

cd simplecrypt-gui/frontend && npm install &&cd ..
cargo tauri dev

Build distributable packages

cargo tauri build

This produces platform-native packages:

• macOS:.dmg
• Windows:.msi
• Linux:.AppImage, .deb

GUI features

• File and directory picker with drag-and-drop
• Password input field
• Algorithm selector dropdown
• Encrypt / Decrypt buttons
• Settings panel (default algorithm, theme, auto-backup)
• Operation status messages

Configuration

SimpleCrypt stores its config as TOML at the platform-specific location:

Platform	Path
macOS	~/Library/Application Support/SimpleCrypt/config.toml
Linux	~/.config/simplecrypt/config.toml
Windows	%APPDATA%\SimpleCrypt\config.toml

Default configuration:

[encryption]
algorithm = "aes-256-gcm"iterations = "adaptive"
[security]
secure_wipe = truebackup_on_encrypt = false
[ui]
theme = "system"

Encrypted File Format

SimpleCrypt v1.5 writes v3.0 JSON envelopes:

{
"version": "3.0",
"algorithm": "aes-256-gcm",
"salt": "<base64>",
"nonce": "<base64>",
"data": "<base64>",
"hmac": "<base64 or null>"
}

• algorithm — identifies which cipher was used
• hmac — present only for non-AEAD algorithms (AES-256-CBC); AEAD algorithms embed authentication in the ciphertext
• Decryption auto-detects v1.0 formats

Running Tests

# Run all tests
cargo test --workspace
# Run core library tests only (21 tests)
cargo test -p simplecrypt-core

Tests cover:

• Round-trip encrypt/decrypt for all 4 algorithms
• Backward compatibility with v1.5 format
• Wrong password rejection
• Tampered data detection
• Cross-algorithm mismatch detection
• Empty, large, and Unicode data handling
• Config save/load round-trip

Security

• Key derivation: PBKDF2-SHA256 with adaptive iterations (10K–600K based on file size)
• Memory safety: Sensitive data (keys, passwords) zeroized after use via the zeroize crate
• Tamper detection: HMAC-SHA256 for CBC mode; built-in authentication tags for AEAD modes
• Timing attack prevention: Constant-time comparisons for HMAC verification
• File permissions: Encrypted files set to 0600 (owner read/write only) on Unix
• Atomic writes: Large files written via temp file + rename to prevent corruption

License

This project is licensed under the MIT License. See the LICENSE file for details.