Using MySQL Enterprise Data Masking and De-Identification To select a random term from a dictionary, use  gen_dictionary() : To select a random term from multiple dictionaries, randomly select one of the dictionaries, then select a term from it: The  gen_blocklist()  function enables a term from one dictionary to be replaced by a term from another dictionary, which effects masking by substitution. Its arguments are the term to replace, the dictionary in which the term appears, and the dictionary from which to choose a replacement. For example, to substitute a US city for a German city, or vice versa, use  gen_blocklist()  like this: If the term to replace is not in the first dictionary,  gen_blocklist()  returns it unchanged: At customer-service call centers, one common identity verification technique is to ask customers to provide their last four Social Security number (SSN) digits. For example, a customer might say her name is Joanna Bond and that her last four SSN digits are  0007 . Using Masked Data for Customer Identification 1581 mysql>  SELECT gen_dictionary(’DE_Cities’); +-----------------------------+ | gen_dictionary(’DE_Cities’) | +-----------------------------+ | Berlin | +-----------------------------+ mysql>  SELECT gen_dictionary(’US_Cities’); +-----------------------------+ | gen_dictionary(’US_Cities’) | +-----------------------------+ | Phoenix | +-----------------------------+ mysql>  SELECT gen_dictionary(ELT(gen_range(1,2), ’DE_Cities’, ’US_Cities’)); +---------------------------------------------------------------+ | gen_dictionary(ELT(gen_range(1,2), ’DE_Cities’, ’US_Cities’)) | +---------------------------------------------------------------+ | Detroit | +---------------------------------------------------------------+ mysql>  SELECT gen_dictionary(ELT(gen_range(1,2), ’DE_Cities’, ’US_Cities’)); +---------------------------------------------------------------+ | gen_dictionary(ELT(gen_range(1,2), ’DE_Cities’, ’US_Cities’)) | +---------------------------------------------------------------+ | Bremen | +---------------------------------------------------------------+ mysql>  SELECT gen_blocklist(’Munich’, ’DE_Cities’, ’US_Cities’); +---------------------------------------------------+ | gen_blocklist(’Munich’, ’DE_Cities’, ’US_Cities’) | +---------------------------------------------------+ | Houston | +---------------------------------------------------+ mysql>  SELECT gen_blocklist(’El Paso’, ’US_Cities’, ’DE_Cities’); +----------------------------------------------------+ | gen_blocklist(’El Paso’, ’US_Cities’, ’DE_Cities’) | +----------------------------------------------------+ | Bremen | +----------------------------------------------------+ mysql>  SELECT gen_blocklist(’Moscow’, ’DE_Cities’, ’US_Cities’); +---------------------------------------------------+ | gen_blocklist(’Moscow’, ’DE_Cities’, ’US_Cities’) | +---------------------------------------------------+ | Moscow | +---------------------------------------------------+