HmacSHA512.java

    /**
     * HmacSHA512
     * 
     * @see <http://drumcoder.co.uk/blog/2011/apr/21/calculate-hmac-hash-java/>
     * @param String value
     * @param String secret
     * @return String
     */
    private String buildHmacSignature(String value, String secret) {
        String result;
        try {
            Mac hmacSHA512 = Mac.getInstance("HmacSHA512");
            SecretKeySpec secretKeySpec = new SecretKeySpec(secret.getBytes(),
                    "HmacSHA512");
            hmacSHA512.init(secretKeySpec);

            byte[] digest = hmacSHA512.doFinal(value.getBytes());
            BigInteger hash = new BigInteger(1, digest);
            result = hash.toString(16);
            if ((result.length() % 2) != 0) {
                result = "0" + result;
            }
        } catch (IllegalStateException | InvalidKeyException | NoSuchAlgorithmException ex) {
            throw new RuntimeException("Problemas calculando HMAC", ex);
        }
        return result;
    }