This field type encrypts the value on create and update. And decrypts on fetch.
This is a Strapi 5 version of the original: https://github.com/Edwin-Luijten/strapi-encryptable-field
I wasn't sure how some things worked in Strapi 5, so this version is missing the Roles dropdown: https://github.com/Edwin-Luijten/strapi-encryptable-field/raw/main/assets/role_based_decryption_settings.png so you can't customise you sees the value
If anyone knows how to do that, go for it, this is a good starting point