Fault-injection attack is a serious threat to the security of cryptographic devices, and various differential fault analysis (DFA) techniques have been presented in the literature over the years. These attacks differ in terms of the underlining assumption on the fault models, the key distinguisher and the complexity of the associated analytical algorithm. In this work, we propose a new DFA technique that uses the inherent bias of the error rates among different signals as the foundation of the key distinguisher design, namely differential error rate analysis (DERA). Compared to existing DFA solutions, DERA is a more efficient and effective attack, in terms of both temporal and spatial needs for the attack, as demonstrated with FPGA emulation in our experiments.