Abstract: An error detection technique can be used with data encryption/decryption such as those implementing the Advanced Encryption Standard (AES) to protect against side-channel attacks known as Differential Fault Analysis attacks, in which the error distribution is unknown. The method uses systematic nonlinear robust error detecting codes which distribute their error-detecting ability substantially uniformly across all possible errors. Error-detecting capabilities of these codes depend not just on error patterns (as in the case of linear codes) but also on data at the output of the device which is protected by the code and this data is unknown to the attacker since it depends on the secret key. The proposed nonlinear (n,k)-codes reduce the fraction of undetectable errors from 2?r to 2?2r as compared to the corresponding (n,k) linear code (where n?k=r and k>=r).