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    <p><strong>1. Random bytes size</strong>: </p> <p>Salts should be at least the same size as your hash function, so for <code>sha256</code> you should use at least 32 bytes. Node.js Crypto's <code>pbkdf2</code> uses <code>SHA1</code>, so 20 bytes should be the minimum. However, the least you should use is <strong>64 bits (8 bytes)</strong>, as explained in #3. (Source: <a href="https://crackstation.net/hashing-security.htm" rel="nofollow noreferrer">https://crackstation.net/hashing-security.htm</a>).</p> <p><strong>2. PBKDF2 number of iterations</strong>: </p> <p>See <a href="https://security.stackexchange.com/questions/3959/recommended-of-iterations-when-using-pkbdf2-sha256">this question</a> for a great discussion. I took from it that <strong>10.000 range</strong> is sufficient without impact performance, but this is hardware/performance dependant.</p> <p><strong>3. PBKDF2 length</strong>:</p> <p>See <a href="https://security.stackexchange.com/questions/31564/key-length-and-hash-function-in-pbkdf2">this other discussion</a> about key lengths. The parameter is again the hashing function used, in your case SHA-1, so 20 bytes is the correct value. Since <a href="http://en.wikipedia.org/wiki/PBKDF2" rel="nofollow noreferrer">PBKDF2's Standard</a> recommends salts of at least <strong>64 bits</strong>, it's a waste to generate keys smaller than your input, so use at least <strong>8 bytes</strong>. Do not use output length of greater than 20, as it provides no additional security, but doubles computation time for each multiple of 20.</p> <p><strong>4. How to store variables</strong>:</p> <p>Discussed in all the links above (especially <a href="https://crackstation.net/hashing-security.htm" rel="nofollow noreferrer">the first</a>), salts should be saved along passwords (but never reused elsewhere), usually by appending it first in the resulting string (salt:hash), or in another database column. </p> <p>As far as other variables, their knowledge is not critical for breaching security (as stated in <a href="https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle" rel="nofollow noreferrer">Kerckhoffs's Principle</a>, so you could parametrize it safely anywhere. Your way of doing it by separating them with "::" is fine, <em>but you are saving extra information</em>. <a href="https://crackstation.net/hashing-security.htm" rel="nofollow noreferrer">Crackstation's codes</a> only save <code>"algorithm:iterations:salt:hash"</code>, so in your case, <strong><code>"salt::derivedKey::iterations"</code></strong> is all you need.</p>
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