Signatures through Approximate Representation by Quadratic Forms. - H. Ong; Claus-Peter Schnorr (CRYPTO, 1983)

Efficient Signature Schemes Based on Polynomial Equations. - H. Ong; Claus-Peter Schnorr; Adi Shamir (CRYPTO, 1984)

An Efficient Signature Scheme Based on Quadratic Equations - H. Ong; Claus-Peter Schnorr; Adi Shamir (STOC, 1984)

An Algorithm for the Computation of Perfect Polyhedral Cones over Real Quadratic Number Fields. - H. Ong; D. Golke (European Conference on Computer Algebra (2), 1985)

Fast Signature Generation With a Fiat Shamir-Like Scheme. - H. Ong; Claus-Peter Schnorr (EUROCRYPT, 1990)