code: private BigInteger coeffGenImproved(Random random, BigInteger modulus)
      {
          BigInteger big;
          int bitLength;
          if (modulus != null)
          {
              bitLength = modulus.bitLength();
          }
          else
          {
              bitLength = 4096;
          }
          // TODO: safety bit?
          bitLength = bitLength - 1;
          big = new BigInteger(bitLength, random);
          return big;
  
      }
docs: Issue#8 fixed coefficient generation