Note:
You can enable data encryption for the Text Box (Single line) fields,. To decrypt the data, you need to disable the Encrypt data property. The process will be similar to enabling it.
Enable data encryption for a field
Open one of your data list, and select a field with the field type as Text Box.
Click "Edit field" to open the "Edit field" window which will appear on the right..
Navigate to the Field Properties > Data Security section.
Check the checkbox next to Encrypt data.
A pop-up window will be display, and you will be prompted:
Click I understand, Proceed. A popup will appear and display the progress of data encryption.