KDF implementation</p>

<h1 id="DESCRIPTION">DESCRIPTION</h1>

<p>The EVP_KDF-SS algorithm implements the Single Step key derivation function (SSKDF). SSKDF derives a key using input such as a shared secret key (that was generated during the execution of a key establishment scheme) and fixedinfo. SSKDF is also informally referred to as &#39;Concat KDF&#39;.</p>

<p>The output is considered to be keying material.</p>

<h2 id="Auxiliary-function">Auxiliary function</h2>

<p>The implementation uses a selectabl