This invention enables authenticated communications (transactions) to take place on a standard I2C bus without requiring modification of existing I2C devices. Read and write transactions occurring on the bus are authenticated using an Authentication Agent and a shared secret key. In addition to allowing verification of the legitimacy of the transactions, the authentication of the I2C transactions enhances the reliability and serviceability of the bus and devices on the bus by allowing the Baseboard Management Controller (BMC) to quickly determine and pinpoint errors.