What is the responsibility of e-commerce merchant to ensure before getting user's consent about his/her details' usage ?

Before getting user's consent about his/her details' usage, the e-commerce merchant must ensure the following:

1. The merchant must clearly state about how the user data will be used, in the terms and conditions of its site.
2. The merchant must ensure that the user has gone through the terms and conditions given on its site prior to making any transactions.
3. The merchant must assure the user about data safety by implementing proper data safety and security measures such as https protocol and other security mechanism so that users' data is safe from hackers too.