Efficient Multivariate Ring Signature Schemes

Multivariate Cryptography is one of the main candidates for creating post-quantum cryptosystems. Especially in the area of digital signatures, there exist many practical and secure multivariate schemes. However, there is a lack of more advanced schemes, such as schemes for oblivious transfer and signature schemes with special properties. While, in the last years, a number of multivariate ring signature schemes have been proposed, all of these have weaknesses in terms of security or efficiency. In this paper we propose a simple and efficient technique to extend arbitrary multivariate signature schemes to ring signature schemes and illustrate it using the example of Rainbow. The resulting scheme provides perfect anonymity for the signer (as member of a group), as well as shorter ring signatures than all previously proposed post-quantum ring signature schemes.