Only use it as an identifier, not as a part of authentication. The issues with using an SSN as a identifier (username) are: 1) Explicitly not meant as an ident

Only use it as an identifier, not as a part of authentication. The issues with using an SSN as a identifier (username) are: 1) Explicitly not meant as an identifier 2) Not unique If not for 2, then the SSN could simply be repurposed to be this identifier.