Using secondary id as foreign key to other table

So I have a Customer table that is linked to different tables. For instance, a Configuration table is linked to Customer table. Instead of using Customer Id as foreign key to the Configuration table, I would like to introduce a secondary id called Reference. This Reference has a value similar to GUID and would like to use this as Foreign Key to the Configuration table. The reason behind this is because I don't want to use the Id of the Customer table. We use integer as a data type for this and I don't want to expose this. What could be the possible complications on implementing this approach?