You can configure repeatable masking for Social Security numbers. To configure repeatable masking for Social Security numbers, click Repeatable Output and choose Seed Value or Mapping Parameter.
When you choose Seed Value, the Designer assigns a random number as the seed. To produce the same Social Security number in different source data, change the seed value in each Data Masking transformation to match the seed value for the Social Security number in the other transformations. If you defined the Data Masking transformation in a mapping, you can configure a mapping parameter for the seed value.
The Data Masking transformation returns deterministic Social Security numbers with repeatable masking. The Data Masking transformation cannot return all unique Social Security numbers because it cannot return valid Social Security numbers that the Social Security Administration has issued.