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This question already has an answer here:

According to Wikipedia:

A rainbow table is ineffective against one-way hashes that include large salts. For example, consider a password hash that is generated using the following function (where "||" is the concatenation operator):
saltedhash(password) = hash(password || salt)
Or
saltedhash(password) = hash(hash(password) || salt)

Say I'm using Argon2(di) to store passwords. Should I use the second method or first method to hash passwords?
And as a more general question, which hash method is typically better in password storage situations? (What about other situations like HMACS?)

marked as duplicate by Luis Casillas, Steffen Ullrich, Overmind, Graham Hill, Benoit Esnard Oct 17 at 23:55

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Say I'm using Argon2(di) to store passwords. Should I use the second method or first method to hash passwords?

No. Argon2 takes the salt as a separate argument from the password, and takes responsibility internally about how to incorporate them both into the computation. As any specialized password hashing function should.

Ideally, though, you should use a higher-level API that takes care of salt generation and management internally, by encapsulating the use of the password hash with:

  • An "enrollment" function that takes a password, generates a salt, and outputs a verification string that encapsulates choice of hashing algorithm, algorithm parameters, salt and hash. See for example the password_hash() in PHP.
  • A "verification" function that takes a password and verification string, parses the latter to recover all those parameters, and verifies that the password matches. See, e.g., password_verify() in PHP.

Basically, if you're manually concatenating salts and passwords like your quote from Wikipedia suggests, you're doing it wrong.

  • I'm definitely not. I'm using Argon2's salt parameter for security. As a separate question: what should I do if I have two salts? Since Argon2 only has one salt input, we get back to the concatenation problem again. – mngxyuiso Oct 12 at 3:11
  • It should be OK to concatenate the two salts into a composite one. If just one of them is unpredictable to an attacker before they see it, so will be the composite. – Luis Casillas Oct 14 at 17:08

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