func (c *WordCodec) BytesToWords(raw []byte) (words []string, err error) {
	// always add a checksum to the data
	data := c.check.AddECC(raw)
	numWords := wordlenFromBytes(len(data))

	n2048 := big.NewInt(2048)
	nData := big.NewInt(0).SetBytes(data)
	nRem := big.NewInt(0)
	// Alternative, use condition "nData.BitLen() > 0"
	// to allow for shorter words when data has leading 0's
	for i := 0; i < numWords; i++ {
		nData.DivMod(nData, n2048, nRem)
		rem := nRem.Int64()
		w := c.words[rem]
		// double-check bank on generation...
		_, err := c.GetIndex(w)
		if err != nil {
			return nil, err
		}
		words = append(words, w)
	}
	return words, nil
}
func (c *WordCodec) BytesToWords(raw []byte) (words []string, err error) {
	// always add a checksum to the data
	data := c.check.AddECC(raw)
	numWords := wordlenFromBytes(len(data))

	n2048 := big.NewInt(2048)
	nData := big.NewInt(0).SetBytes(data)
	nRem := big.NewInt(0)
	// Alternative, use condition "nData.BitLen() > 0"
	// to allow for shorter words when data has leading 0's
	for i := 0; i < numWords; i++ {
		nData.DivMod(nData, n2048, nRem)
		rem := nRem.Int64()
		w := c.words[rem]
		// double-check bank on generation...
		_, err := c.GetIndex(w)
		if err != nil {
			return nil, err
		}
		words = append(words, w)
	}
	return words, nil
}
// TODO: add checksum