CLAVEM

Secure file encryption tool for long-term data protection.

by Massimo Parisi (antaresfil)
📧 clavemhelp@noxfarm.com  |  🛠️ Support: clavemhelp@noxfarm.com

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What is CLAVEM?

CLAVEM is a Windows desktop application that encrypts files and folders using modern, authenticated cryptography. It is designed for users who want strong, local, offline protection for sensitive data — with no cloud, no accounts, and no backdoors.

Every encrypted file becomes a .svlt container. Without the correct password (and keyfile, if used), the content is computationally unrecoverable.

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Features

• 🔒 AES-256-GCM — authenticated encryption (confidentiality + integrity in one pass)
• 🔑 Argon2id key derivation — memory-hard, GPU/ASIC resistant (OWASP recommended)
• 📎 Optional keyfile — cryptographic second factor derived from file content only (name and path are ignored)
• 🗂️ File and folder encryption — folders are packaged as ZIP then encrypted in a single .zip.svlt
• 🗑️ 3-pass secure delete — optional DoD-style overwrite of the original after encryption
• 🛡️ Privacy-preserving design — CLAVEM never stores or reveals whether a keyfile was used
• ✅ Legacy compatibility — reads SVLT v1, v2, and v3 containers
• 🖥️ DPI-aware UI — PerMonitorV2 manifest, ClearType rendering on all displays

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Cryptographic Design

Component	Algorithm	Notes
Encryption	AES-256-GCM	128-bit authentication tag
Key Derivation	Argon2id	64 MiB · 3 iterations · 4 lanes
Salt	256-bit random	Per-file, generated via OS CSPRNG
Nonce	96-bit random	Per-file, generated via OS CSPRNG
Keyfile hashing	SHA-256	Content-only — path and filename ignored

Master key construction:

Password only:         M = UTF8(password)
Password + Keyfile:    M = UTF8(password) || 0x00 || SHA-256(keyfile_bytes)

M is then passed to Argon2id with a per-file random salt to derive the AES-256-GCM key.

SVLT v3 container layout:

[4 bytes]  Magic: "SVLT"
[1 byte ]  Version: 3
[32 bytes] Salt (Argon2id)
[12 bytes] Nonce (AES-GCM)
[16 bytes] Authentication Tag (GCM)
[n bytes ] Ciphertext  ← includes original filename inside encrypted payload

In v3, the filename is protected inside the ciphertext — not stored in the cleartext header.
The entire header is authenticated as AAD: any tampering causes immediate decryption failure.

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Security Fixes in v2.0.2

#	Issue	Severity	Status
1	Master-key zeroing bug — DeriveMasterKey returned an already-zeroed buffer	Critical	✅ Fixed
2	Integer overflow on payload sizing near 2 GB	High	✅ Fixed
3	Infinite loop in SecureDelete on 0-byte files	Medium	✅ Fixed
4	Crash in metadata reader when file disappears mid-read	Low	✅ Fixed
5	Duplicate error dialogs from nested try/catch	Low	✅ Fixed
6	Keyfile bytes lived in memory for entire operation duration	Low	✅ Fixed (v2.0.2)

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Threat Model

CLAVEM protects against:

• Offline attackers who obtain .svlt files and attempt brute-force decryption
• Ciphertext tampering (detected by the GCM authentication tag)
• Filename disclosure (filename is inside the ciphertext in v3)
• Malicious ZIP entries during folder decryption (Zip Slip protection)

CLAVEM does NOT protect against:

• Compromised endpoints (keyloggers, malware with memory access)
• RAM forensics during active operation
• Weak or guessable passwords

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Known Limitations

These are platform constraints, not implementation defects.

• Secure Delete on SSD/NVMe — wear leveling may prevent physical overwrite of original sectors. Use full-disk encryption (e.g. BitLocker) for high-assurance requirements.
• Folder mode — a temporary ZIP is created before encryption. It is securely deleted after the operation.
• File size — files larger than 2 GB are not supported (in-memory design).

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Build

Requirements

• Windows 10 / 11 (64-bit)
• .NET 8.0 SDK
• Visual Studio 2022 (optional) or dotnet CLI

CLI

dotnet restore
dotnet build -c Release
dotnet run

Included scripts

Script	Purpose
build.bat	Standard debug build
create-portable-release.bat	Builds a self-contained portable release
create-source-package.bat	Packages source for distribution

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Project Structure

CLAVEM/
├── CryptoEngine.cs            # AES-256-GCM, Argon2id, SecureDelete, SVLT format
├── AuthenticationManager.cs   # Master key construction (password + optional keyfile)
├── MainWindow.xaml / .cs      # UI + async execution pipeline
├── FolderCryptoHelper.cs      # Folder analysis, ZIP, Zip Slip-safe extraction
├── SecureLogger.cs            # Append-only audit log (no sensitive data)
├── FileMetadata.cs            # Privacy-preserving SVLT metadata reader
├── FolderPicker.cs            # Windows folder dialog
├── Resources/
│   ├── clavem.ico             # Application icon (transparent background)
│   └── clavem_logo.png        # Logo
├── app.manifest               # PerMonitorV2 DPI awareness
└── Clavem.csproj

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Dependencies

Package	Version	Purpose
Konscious.Security.Cryptography.Argon2	1.3.0	Argon2id implementation
.NET 8.0 BCL	built-in	AES-GCM, SHA-256, RandomNumberGenerator, SecureString
System.IO.Compression	built-in	ZIP for folder encryption mode

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License

CLAVEM is dual-licensed:

• AGPL-3.0-only — free for personal and open-source use
• Commercial license — for closed-source or proprietary distribution

For commercial licensing: xilomen@gmail.com

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Security Disclosures

See SECURITY.md for the responsible disclosure process.

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Release Integrity

v2.0.2 source package SHA-256:

9a72d9d3e7e6fe58586b188f256592bfe8856a0ae9f7370eac60935c9d685dc4

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Made with ❤️ for secure file protection
Massimo Parisi (antaresfil) · clavemhelp@noxfarm.com