it is ok not to sign on the back of the card when you hold the card, and it is also ok not to sign the card without a password. However, I suggest signing. Although some people think that it is safer not to sign, the safer here means that the specific responsibility sharing may have a certain advantage because the cardholder does not sign, but the most important thing for credit card security is to prevent stealing, not how to allocate responsibility after stealing, so signing is safer.