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Cryptography

The simulator implements a hybrid encryption scheme that mirrors what LockBit 3.0, Conti, and REvil use in production. RSA handles key transport. AES handles data. Per-file keys mean that cracking one file's key doesn't affect any other.

Hybrid Encryption Scheme

flowchart TD
    A["C2 generates RSA-2048 key pair"] --> B["Public key delivered at registration"]
    B --> C["Per file: generate AES-256 key + 96-bit nonce"]
    C --> D["AES-256-GCM encrypt file"]
    D --> E["RSA-OAEP wrap AES key"]
    E --> F["Write: wrapped_key + nonce + ciphertext"]
    F --> G["OPENSSL_cleanse original from memory"]
    G --> H["Exfiltrate wrapped keys to C2"]
    H --> I["Recovery requires C2 RSA private key"]
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Encryption Flow

sequenceDiagram
    participant Client
    participant C2

    Client->>C2: POST /api/register
    C2-->>Client: victim_id + RSA-2048 public key

    loop Per file
        Client->>Client: Generate AES-256 key + nonce
        Client->>Client: AES-256-GCM encrypt
        Client->>Client: RSA-OAEP wrap AES key
    end

    Client->>C2: POST /api/exfiltrate (wrapped keys)
    C2-->>Client: stored

    loop Every 60s
        Client->>C2: GET /api/command
        C2-->>Client: encrypt / decrypt / idle
    end

    Client->>C2: fetch wrapped keys
    C2-->>Client: keys decrypted with RSA private key
    Client->>Client: restore files
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Algorithms

Layer Algorithm Key Size Notes
Asymmetric RSA-OAEP 2048-bit Key transport only
Symmetric AES-GCM 256-bit Authenticated encryption
Nonce CSPRNG 96-bit Unique per file
Auth tag GCM 128-bit Detects tampering

AES-GCM provides authenticated encryption - the auth tag means a modified ciphertext will fail decryption rather than producing corrupted plaintext. This is intentional and matches what real ransomware uses to prevent victims from tampering with encrypted files.

Secure Memory Management

Key material is handled through RAII wrappers that call OPENSSL_cleanse() on destruction. Keys do not persist in memory after their scope exits.

{
    Crypto::SecureKey256 key;            // 32-byte AES key on stack
    generate_key(key.data(), key.size());
    encrypt_file(path, key.to_vector());
}
// OPENSSL_cleanse() called automatically here

This mirrors documented behavior in LockBit 3.0 (OPENSSL_cleanse) and Conti (SecureZeroMemory). Forensic key recovery from a memory dump is not possible after scope exit.

Intermittent Encryption

Modern ransomware families encrypt partially rather than fully - faster execution, lower CPU/disk usage, harder to detect behaviorally.

Mode Behavior Detection Difficulty
FULL Encrypt entire file Baseline
HEADER_ONLY First 4MB only Higher - breaks headers, files appear corrupt
INTERMITTENT Header + every 16th chunk Highest - evades time and CPU behavioral rules

With INTERMITTENT mode, randomized chunk intervals are supported to defeat static pattern analysis. This is the LockBit 3.0 technique documented in public threat intelligence reports.

Ransomware Comparison

Family Symmetric Asymmetric Notes
This simulator AES-256-GCM RSA-2048
LockBit 3.0 AES-256 RSA-2048 Intermittent encryption
Conti AES-256 RSA-4096 Double extortion
REvil Salsa20 Curve25519 / ECDH RaaS model
BlackCat ChaCha20 RSA-4096 Written in Rust
Ryuk AES-256 RSA-4096 Big game hunting
DarkSide Salsa20 RSA-1024 Colonial Pipeline