code: function computeVerifier(params, salt, I, P) {
    assertIsBuffer(salt, "salt (salt)");
    assertIsBuffer(I, "identity (I)");
    assertIsBuffer(P, "password (P)");
    var v_num = params.g.powm(getx(params, salt, I, P), params.N);
    return padToN(v_num, params);
  }
docs: /*
  The verifier is calculated as described in Section 3 of [SRP-RFC].
  We give the algorithm here for convenience.
  
  The verifier (v) is computed based on the salt (s), user name (I),
  password (P), and group parameters (N, g).
  
  x = H(s | H(I | ":" | P))
  v = g^x % N
  
  params:
  params (obj)     group parameters, with .N, .g, .hash
  salt (buffer)    salt
  I (buffer)       user identity
  P (buffer)       user password
  
  returns: buffer