...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 of giving you the actual key, it gives you a safe containing the key. This approach allows the hash latch to protect itself from forged keys and also enables you to put the same key into multiple safes without the recipients of these safes knowing they have the same key (even if they compare their ciphertexts).
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