A security mechanism for one-time secured data access, using re-writable/readable contactless tags with corresponding software and hardware implementations to provide a multi-layered one-time secured trading/service for various business transaction modes, such as business-to-business (B2B), business-to-consumer (B2C), and homo/hetero-business, so that information security of a company, a government department, or even a person can be enhanced while the complexity of data security control is greatly reduced.