The hash latch generates keys in a manner similar to how some cryptocurrencies are mined. It takes a string and brute-forces a prefix for it so that the hash of the string with the prefix has a certain number of leading zeroes.
But that alone would've been too easy to hack.
To prevent an attacker from forging the keys by generating a new prefix: the hash latch doesn't output the keys in the plaintext. Instead, it encrypts the key and outputs the ciphertext. That means that instead...