Cryptography is a well-established science that has been a significant historical influence for more than 2,000 years. Traditionally its main users were governments and the military, although it is worth noting that The Kama Sutra of Vatsyayana contains a recommendation that women should study the art of understanding writing in cypher (full details of all works cited are given in References and further reading.-Cryptography is a well-established science that has been a significant historical influence for more than 2,000 years. Traditionally its main users were governments and the military, although it is worth noting that The Kama Sutra of Vatsyayana contains a recommendation that women should study　the art of understanding writing in cypher　(full details of all works cited are given in References and further reading.