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Assuming I had to distribute salt+ciphertext together over an insecure channel, isn't it better to store the salt encrypted?

By encrypted I mean with a block cipher and with key and IV derived from the same passphrase used to encrypt the original text.

I've been told that leaving salt unencrypted is the way to go. Why? Why not encrypt? Isn't it always better?

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  • $\begingroup$ Encrypting the salt either uses another salt, or lets an attacker use pre-computation $\hspace{1.5 in}$ for the first part of each decryption attempt. $\:$ $\endgroup$ – user991 Aug 30 '12 at 5:28
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No, it is not better. To send the salt encrypted, one would need a key and IV (another salt) to encrypt it. This adds unnecessary complexity as the security of the ciphertext does not depend on the salt being kept private. So, encrypting the salt adds negligible security yet adds a fair amount of complexity. Keeping things as simple as possible is often a good rule of thumb.

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