When you configure a column for key masking, the Data Masking transformation creates a seed value for the column. You can change the seed value to produce repeatable data between different Data Masking transformations. For example, configure key masking to enforce referential integrity. Use the same seed value to mask a primary key in a table and the foreign key value in another table.

You can configure masking rules that affect the format of data that the Data Masking transformation returns. You can mask numeric, string, and datetime data types with key masking.

When you can configure key masking for datetime values, the Data Masking transformation requires a random number as a seed. You can change the seed to match the seed value for another column to return repeatable datetime values between the columns. The Data Masking transformation can mask dates between 1753 and 2400 with key masking. If the source year is in a leap year, the Data Masking transformation returns a year that is also a leap year. If the source month contains 31 days, the Data Masking transformation returns a month that has 31 days. If the source month is February, the Data Masking transformation returns February. The Data Masking transformation always generates valid dates.

Configure key masking for numeric source data to generate deterministic output. When you configure a column for numeric key masking, you assign a random seed value to the column. When the Data Masking transformation masks the source data, it applies a masking algorithm that requires the seed.

You can configure key masking for strings to generate repeatable output. Configure a mask format to define limitations for each character in the output string. To define a mask format, configure the Source Filter characters and the Target Filter characters. The source filter characters define the source characters to mask. The target filter characters define the characters to mask the source filter characters with.