I think it’ll generate 5 days converted into seconds number of operations.
To decrypt however, you have to do all those operations, so I think it would take 5 days to decrypt. Even if you wait 10 days to start the operation
def generate_proof_of_work_key(initial_key, time_seconds):
proof_key = initial_key
end_time = time.time() + time_seconds
iterations = 0
while time.time() < end_time:
proof_key = scrypt(proof_key, salt=b'', N=SCRYPT_N, r=SCRYPT_R, p=SCRYPT_P, key_len=SCRYPT_KEY_LEN)
iterations += 1
print(f"Proof-of-work iterations (save this): {iterations}")
return proof_key
def generate_proof_of_work_key_decrypt(initial_key, iterations):
proof_key = initial_key
for _ in range(iterations):
proof_key = scrypt(proof_key, salt=b'', N=SCRYPT_N, r=SCRYPT_R, p=SCRYPT_P, key_len=SCRYPT_KEY_LEN)
return proof_key
The first function is used during the encryption process, and the while loop clearly runs until the specified time duration has elapsed. So encryption would take 5 days no matter how fast your computer is, and to decrypt it, you’d have to do the same number of iterations your computer managed to do in that time. So if you do the decryption on the same computer, you should get a similar time, but if you use a different computer that is faster at doing these operations, it will decrypt it faster.
What is the threat szenario?
If you are smart about parallelization and have access to custom hardware, couldn’t you turn 5 days into 1 hour or less?
Yes, that’s exactly the problem - there’s nothing wrong with the encryption used, but it’s IMHO incorrect to call it time-based when it’s “work-based” and it just so happens that the specific computer doing the encryption works at a given speed.
I don’t call my laptop’s FDE time-based encryption just because I picked an encryption that takes it 10 seconds to decrypt the key.
