[jstanley]

> A 2020 MacBook Air can hash every North American phone number in four hours

If you added a salt, this would still allow you to reverse some particular hashed phone number in about 4 hours, it just wouldn't allow you to do all of them at the same time.

[OutOfHere]

I do not agree. How will you reverse a salt with sufficient entropy? Imagine the salt is a 512 bit hex, the data is a ten decimal digit phone number, the generated hash is 512 bits of which the first 160 bits are used as the value. Now exactly how will you get the phone number back? Do you really think you can iterate over half of the possibilities of 512 bits in four hours?

[jstanley]

You know the salt because it's stored alongside the hash. You're only iterating over the space of phone numbers.

If it's not stored alongside the hash it's not a salt, it's something else.

https://en.wikipedia.org/wiki/Salt_(cryptography)

[OutOfHere]

> If it's not stored alongside the hash it's not a salt, it's something else.

That is not even true. The definition in the article does not substantiate it. There is no requirement for the salt to be stored alongside the hash.

The definition in the article is sufficiently clear. This is all that a salt is:

> a salt is random data fed as an additional input to a one-way function that hashes data

With regard to effective anonymization, the salt is stored by the generator, but not in the exported dataset.

[jstanley]

If the "salt" is kept secret then I agree you can't brute force all the phone numbers so easily. But I don't agree that "salt" is the correct term for that technique.