Transactions today are conducted in a way that leaves no real option to the customers to protect their privacy. Sensitive private information is left uncontrolled at the companies' disposal and is often (un) intentionally leaked to unauthorized parties. There is a growing demand for privacy-preserving management of private information that will make individuals feel safer during their transactions and assist companies with customer data management. In this work we propose that individuals store and manage their transaction data locally, in a personal portfolio, allowing them to retain control of their private information. Using contemporary cryptographic techniques, companies are given access to the accountable, certified data of portfolios in a privacy-preserving way.