Wikipedia
Vātsyāyana is the name of a Hindu philosopher in the Vedic tradition who is believed to have lived around 2nd century AD in India. His name appears as the author of the Kama Sutra. Not to be confused with Pakṣilasvāmin Vātsyāyana, the author of Nyāya Sutra Bhāshya, the first preserved commentary on Gotama's Nyāya Sutras.
His name is sometimes confused with Mallanaga, the prophet of the Asuras, to whom the origin of erotic science is attributed. This is an error; as Daniélou says:
Hardly anything is known about him, although it is believed that his disciples went on his instructions, on the request of the Hindu Kings in the Himalayan range to influence the hill tribals to give up the pagan cult of sacrifices. He is said to have created the legend of Tara among the hill tribes as a tantric goddess. Later as the worship spread to the east Garo hills,the goddess manifest of a 'yoni' goddess Kamakhya was created. His interest in human sexual behavior as a medium of attaining spirituality was recorded in his treatise Kama Sutra.
At the close of the Kama Sutra this is what he writes about himself:
After reading and considering the works of Babhravya and other ancient authors, and thinking over the meaning of the rules given by them, this treatise was composed, according to the precepts of the Holy Writ, for the benefit of the world, by Vatsyayana, while leading the life of a religious student at Benares, and wholly engaged in the contemplation of the Deity. This work is not to be used merely as an instrument for satisfying our desires. A person acquainted with the true principles of this science, who preserves his Dharma (virtue or religious merit), his Artha (worldly wealth) and his Kama (pleasure or sensual gratification), and who has regard to the customs of the people, is sure to obtain the mastery over his senses. In short, an intelligent and knowing person attending to Dharma and Artha and also to Kama, without becoming the slave of his passions, will obtain success in everything that he may do.
It is impossible to fix the exact date either of the life of Vatsyayana or of his work. It is believed that he must have lived between the 1st and 6th century AD, on the following grounds: He mentions that Satakarni Satavahana, a king of Kuntal, killed Malayevati his wife with an instrument called Katamari by striking her in the passion of love. Vatsyayana quotes this case to warn people of the danger arising from some old customs of striking women when under the influence of sexual passion. This king of Kuntal is believed to have lived and reigned during the 1st century AD, and consequently Vatsyayana must have lived after him. On the other hand, another author, Varahamihira, in the eighteenth chapter of his "Brihatsanhita", discusses of the science of love, and appears to have borrowed largely from Vatsyayana on the subject. Varahamihira is believed to have lived during the 6th century, and therefore Vatsyayana must have written his works before the 6th century.
Vatsyayana's Kama Sutra describes techniques of cryptography.