public static String encryptMD5(String secret, String data) {
        return encryptMD5(secret + ":" + data);
    }
Defined in rfc 2617 as KD(secret, data) = H(concat(secret, ":", data))

@param data data
@param secret secret
@return H(concat(secret, ":", data));
pac4j-http/src/main/java/org/pac4j/http/credentials/CredentialUtil.java