Cryptanalysis and modification of digital signature scheme based on error-correcting code

W. Xinmei (see ibid., vol.26, no.13, p.898-9, 1990) proposed a digital signature scheme based on the error-correcting code. The authors point out that in the Xinmei scheme it is possible to combine valid signatures of messages into a valid signature of another message in polynomial time even when the factoring of large matrices is unknown. Some modifications are suggested to improve the security and performance.