The issue is that you can parallelize the "unlocking" operation. So, if one person is attempting to unlock, they solve in 10 years. If two people attempt, it'

The issue is that you can parallelize the "unlocking" operation. So, if one person is attempting to unlock, they solve in 10 years. If two people attempt, it's solved in 5 years. If the NSA puts all their computers on it, it takes 1 second. The author is proposing methods that are forcibly sequential.