Construction of MDS self-dual codes from orthogonal matrices
  In this paper, we give algorithms and methods of construction of self-dual codes over finite fields using orthogonal matrices. Randomization in the orthogonal group, and code extension are the main tools. Some optimal, almost MDS, and MDS self-dual codes over both small and large prime fields are constructed. 
Minjia Shi, Lin Sok, Patrick Sol\'e
cs.IT math.IT