I have several concept questions about encrypting data.

The task

My goal is to encrypt NVARCHAR(3800) column but I want to encrypt only small percent of the data (less than 1% of it). As the table is referred in so many SQL objects, ASP files, .rdl files and SSIS projects I do not want to create separate table to hold these values there (at least for now I am looking for alternatives).

The plan

I am thinking for one of the following solution:

1. Add bit column to the table called isEncrypted with default constraint 0 and with values
2. Rename the current column to _column_raw_data
3. Add new column called _column_encrypted_data
4. Add new computed column with the original column name _column which will return the _column_raw_data if IsEncrypted flag is 0, otherwise the _column_encrypted_data
5. By default a query will return encrypted data – in order to decrypt it, additional logic will be implemented

or I am wondering is there any considerations to:

1. Add bit column to the table called isEncrypted with default constraint 0 and with values
2. When data is going to be encrypted the flag is raised and the output encrypted varbinary value will be set in the existing column

I am going to test the both variants of course but before doing that I am wondering is there another option or any issues in the above ones?