A tokenization system tokenizes sensitive data to prevent unauthorized entities from accessing the sensitive data. The tokenization system accesses sensitive data, and retrieves an initialization vector (IV) from an IV table using a first portion of the sensitive data. A second portion of the sensitive data is modified using the accessed initialization vector. A token table is selected from a set of token tables using a third portion of the sensitive data. The modified second portion of data is used to query the selected token table, and a token associated with the value of the modified second portion of data is accessed. The second portion of the sensitive data is replaced with the accessed token to form tokenized data.