An encrypted search index is disclosed. For instance, an exemplary system may include a search index stored on disk with customer information stored therein, the search index files having a term dictionary or a term index type file having internal structure which allows a portion of the individual search index file to be updated, encrypted, and/or decrypted without affecting the internal structure of the individual search index file; a file input/output (IO) layer to encrypt the customer information being written into the individual search index file and to decrypt the customer information being read from the individual search index file; and a query interface to execute the operation against the customer information stored in the memory in its decrypted form.