1. Shigeo Tsujii, Kohtaro Tadaki, and Ryou Fujita, Proposal for piece in hand matrix: General concept for enhancing security of multivariate public key cryptosystems, IEICE Trans A: Fundamentals E90-A (2007), no. 5, 992-999.[doi]
  2. Shigeo Tsujii, Kohtaro Tadaki, and Ryou Fujita, Nonlinear piece-in-hand matrix method for enhancing security of multivariate public key cryptosystems, IACR (2008).[eprint]