Arculus does not use a simple NTAG chip, instead it uses a secure element with a best-in-class CC EAL6+ Hardware Classification, similar to ones in banking cards and passports. Multiple layers of physical and software security keep your private keys safe. Arculus also uses encrypted proprietary NFC communication between your phone and the card with constantly changing keypairs, and this communication also does not contain any address or amount information. This means there is also no way for a 'man in the middle' attack.