13. A computer system for creating index information for an e-book having content, the computer system comprising: a non-transitory computer-readable storage medium storing executable computer program instructions, the computer program instructions comprising instructions for: identifying logical partitions of the e-book content, the content comprising a plurality of phrases located within one or more of the logical partitions; creating a plurality of encrypted segments for the e-book, each segment comprising a subset of the e-book content; storing index information including a mapping between the phrases located within the one or more logical partitions and the plurality of encrypted segments, the mapping indicating, for a phrase, one or more encrypted segments that include the phrase; and providing the encrypted segments for the e-book and the index information to an eReader device, wherein the eReader device is adapted to receive a search query for a search phrase from a user of the eReader device, use the index information to identify one or more encrypted segments that include the search phrase, and, responsive to receiving the search query, decrypt only the one or more encrypted segments that include the search phrase; and a processor for executing the computer program instructions.
13. A computer system for creating index information for an e-book having content, the computer system comprising: a non-transitory computer-readable storage medium storing executable computer program instructions, the computer program instructions comprising instructions for: identifying logical partitions of the e-book content, the content comprising a plurality of phrases located within one or more of the logical partitions; creating a plurality of encrypted segments for the e-book, each segment comprising a subset of the e-book content; storing index information including a mapping between the phrases located within the one or more logical partitions and the plurality of encrypted segments, the mapping indicating, for a phrase, one or more encrypted segments that include the phrase; and providing the encrypted segments for the e-book and the index information to an eReader device, wherein the eReader device is adapted to receive a search query for a search phrase from a user of the eReader device, use the index information to identify one or more encrypted segments that include the search phrase, and, responsive to receiving the search query, decrypt only the one or more encrypted segments that include the search phrase; and a processor for executing the computer program instructions. 16. The computer system of claim 13 , wherein the instructions for identifying logical partitions of the e-book further comprise instructions for: analyzing the content of the e-book to determine textual characteristics indicating boundaries; and using the boundaries indicated by the textual characteristics as boundaries of the logical partitions.