encrypted fields - email

just curious why a text field holding an email address cannot be encrypted. I understand the rest, being able to encrypt this would be good for privacy and security.

  • Special fields (such as primary key, foreign key, username, password, email, user ID/Level/Profile/Activate) will not be encrypted

I believe for performance reason. Imagine when your encrypt – for example, the primary key field — then system must decrypt it back and the proceed the next process.