Slave device and computer readable medium

A non-transitory computer readable medium storing a slave program for causing a computer to execute:

• a reception process of receiving a frame destined for a master located on an upstream side from a slave located on a downstream side;
• an intermediate-computation-result calculation process of calculating an intermediate computation result, using a received message authentication code, which is a message authentication code included in the received frame, the intermediate computation result being obtained by computing a part of a computation expression for calculating the received message authentication code;
• a transmission data concatenation process of concatenating transmission data, which is to be transmitted to the master, to a transmission data string included in the received frame;
• a message authentication code calculation process of calculating a message authentication code for a concatenated transmission data string, using the intermediate computation result;
• a concatenation determination process of determining whether data concatenation is allowed, based on a transmission source address of the received frame;
• and
• a transmission process of transmitting a frame including the concatenated transmission data string and including the message authentication code calculated using the intermediate computation result, instead of the received message authentication code, to the upstream side when it is determined that data concatenation is allowed, and transmitting the received frame to the upstream side when it is determined that data concatenation is not allowed.