The Kamasutra (Vatsyayana) cipher is a simple substitution cipher where the 26 letters of the alphabet are organized into 13 pairs of characters. These pairs are then used to encrypt the text by direct substitution of the letters in the pairs. You'll want to use unique pairs for the encryption. This type of cipher is a form of symmetric encryption as the same key can be used to both encrypt and decrypt a message.
Encryption Key Pairs