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Key Management Patterns in Ransomware:
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1. STRONG (no recovery possible without key):
   - Per-file AES key generated with CryptGenRandom
   - AES key encrypted with embedded RSA public key
   - Encrypted key appended to each file or stored separately
   - RSA private key held only by attacker's C2 server

2. WEAK (potential recovery):
   - AES key derived from predictable seed (timestamp, PID)
   - Same AES key used for all files (single key compromise = full recovery)
   - Key transmitted to C2 before encryption starts (PCAP may contain key)
   - XOR with short repeating key (brute-forceable)
   - PRNG seeded with GetTickCount or time() (limited keyspace)

3. FLAWED IMPLEMENTATION:
   - ECB mode (preserves plaintext patterns)
   - Initialization vector (IV) reuse across files
   - Key stored in plaintext in memory (recoverable from memory dump)
   - Partial encryption (only first N bytes encrypted)

// Typical ransomware file encryption flow (decompiled pseudo-code from Ghidra):

void encrypt_file(char *filepath) {
    // 1. Check file extension against target list
    if (!is_target_extension(filepath)) return;

    // 2. Generate per-file AES key (32 bytes for AES-256)
    BYTE aes_key[32];
    CryptGenRandom(hProv, 32, aes_key);

    // 3. Generate random IV (16 bytes)
    BYTE iv[16];
    CryptGenRandom(hProv, 16, iv);

    // 4. Read file contents
    HANDLE hFile = CreateFile(filepath, GENERIC_READ, ...);
    BYTE *plaintext = read_entire_file(hFile);

    // 5. Encrypt with AES-256-CBC
    aes_cbc_encrypt(plaintext, file_size, aes_key, iv);

    // 6. Encrypt AES key with RSA public key
    BYTE encrypted_key[256];  // RSA-2048 output
    rsa_encrypt(aes_key, 32, rsa_pubkey, encrypted_key);

    // 7. Write: encrypted_data + encrypted_key + IV to file
    write_file(filepath, encrypted_data, encrypted_key, iv);

    // 8. Rename file with ransomware extension
    rename_file(filepath, strcat(filepath, ".locked"));
}

from Crypto.Cipher import AES
import os
import struct

# Extract IVs (location depends on ransomware family)
# If IVs are same and files share encrypted blocks -> same key
iv1 = data1[-16:]  # Example: IV at end
iv2 = data2[-16:]
if iv1 == iv2:
    print("[!] Same IV detected - key reuse likely")

for ts in timestamp_range:
    # Derive key the same way ransomware does
    import hashlib
    key = hashlib.sha256(str(ts).encode()).digest()
    iv = encrypted_data[-16:]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    decrypted = cipher.decrypt(encrypted_data[:16])

    if decrypted[:len(known_header)] == known_header:
        print(f"[!] Key found! Timestamp: {ts}")
        return key

return None

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key = bytes(c ^ p for c, p in zip(ciphertext, known_plaintext))
# Find repeating key length
for key_len in range(1, 256):
    candidate = key[:key_len]
    if all(key[i] == candidate[i % key_len] for i in range(min(len(key), key_len * 4))):
        print(f"XOR key (length {key_len}): {candidate.hex()}")
        return candidate
return None

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Analysis should document:
- Algorithm identified (AES, RSA, ChaCha20, custom)
- Key size and mode of operation (CBC, CTR, ECB, GCM)
- Key generation method (CSPRNG, predictable seed, static key)
- Key storage location (appended to file, registry, C2 transmission)
- File modification pattern (full encryption, partial, header-only)
- Targeted file extensions
- Ransom note format and payment infrastructure
- Decryption feasibility assessment (possible/impossible/partial)
- Recommended recovery approach

RANSOMWARE ENCRYPTION ANALYSIS
================================
Sample:           lockbit3.exe
Family:           LockBit 3.0 / LockBit Black
SHA-256:          abc123def456...

ENCRYPTION SCHEME
File Cipher:      AES-256-CTR (per-file unique key)
Key Wrapping:     RSA-2048 (public key embedded in binary)
Key Generation:   CryptGenRandom (CSPRNG - unpredictable)
IV Generation:    Random 16 bytes per file
File Structure:   [encrypted_data][rsa_encrypted_key(256B)][iv(16B)][magic(8B)]

TARGETED EXTENSIONS
Total:            412 extensions targeted
Categories:       Documents (.doc, .xls, .pdf), Databases (.sql, .mdb),
                  Archives (.zip, .7z), Source code (.py, .java, .cs)
Excluded:         .exe, .dll, .sys, .lnk (system files preserved)

IMPLEMENTATION ANALYSIS
Key Strength:     STRONG - per-file random keys, no reuse
Mode Security:    STRONG - CTR mode with unique nonces
Key Storage:      RSA-encrypted key appended to each file
Shadow Copies:    Deleted via vssadmin and WMI

DECRYPTION FEASIBILITY
Without Key:      NOT POSSIBLE
  - No implementation flaws identified
  - RSA-2048 key wrapping prevents brute force
  - CSPRNG prevents key prediction
  - No existing free decryptor available

RECOVERY OPTIONS
1. Restore from offline backups (recommended)
2. Check for volume shadow copies (low probability - ransomware deletes them)
3. Memory forensics if machine was not rebooted (key may persist in RAM)
4. Negotiate with attacker (last resort - no guarantee of decryption)