Disclosed are a method and apparatus capable of reducing the number of computations required to generate a digital signature by a digital signature generator. A digital signature generator generates a code word for a received message by a function F for generating a code word having a set weight value and generates a digital signature based on the generated code word and an inverse of a public parity check matrix H, the parity check matrix H is one way function. A digital signature receiver converts the received message using the function F for generating a code word, and multiplies a public parity check matrix H by a received digital signal, the public parity check matrix H is a one way function, and comparing the converted value with the multiplication result.