Chachaware
An educational ransomeware experiment. It doens't contact any servers when encrypting a target and easily maxes out disk IO. The following things where the design goals:
- Don't contact any servers but allow recovery.
- Encrypt the target as fast as possible using chacha and a goroutine pool.
- Use modern cryptography to make recovery without key as difficult as possible.
How does it work?
When chachaware is started it does the following things:
- Generate a random X25519 key pair. (recoveryPriv, recoveryPub)
- Do a key exchange with a stored X25519 public key. (storedPub)
- Forget the recoveryPriv and store the recoveryPub.
- Use HKDF with sha256 on the result of the key exchange(storedPub, recoveryPriv) and use the result as the secret to encrypt the files.
- Then start scanning the disk for target files and encrypt them using chacha20. (without poly1305 because we don't need authentication but do need performance)
Recovery
Recovering the secret is possible using the following steps:
- Send the recoveryPub to the distributor.
- The distributor will do a key exchange between recoveryPub and storedPriv.
- After doing HKDF with sha256 the secret is recovered.
- Decrypt the files using the secret.
Possible improvements
- Use snappy to compress files before encrypting. This would move some of the work from the disk to the cpu and would probably speed up chachaware by ~20-80%