LockBit 4.0 Encryption Scheme: Key Exchange Dissection

By Tech Ordus Research April 12, 2026 ransomware

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Key Hierarchy

LockBit 4.0 implements a three-tier key architecture:

Operator keypair (ECDH P-256): embedded in binary at compile time
Victim keypair: generated on first run, private key wrapped with operator public key
File encryption key (FEK): unique AES-256 key per file, wrapped with victim public key

Encryption Flow

for each file:
  fek = random_bytes(32)
  iv  = random_bytes(16)
  encrypted_data = AES-CTR(fek, iv, file_content)
  wrapped_fek    = ECDH_encrypt(victim_pubkey, fek)
  append(wrapped_fek || iv || encrypted_data)

Recovery Constraints

Without the operator private key, recovery requires brute-forcing the 256-bit FEK per file — computationally infeasible. Backup restoration from offline snapshots created before T-0 is the only reliable path.

Detection Windows

The highest-fidelity detection opportunity is during the pre-encryption phase:

Shadow copy deletion via vssadmin delete shadows /all /quiet
Backup catalog deletion via wbadmin delete catalog
Service termination of AV/EDR products