Abstract. We demonstrate two classes of attacks on EC-RAC, a growing set of RFID protocols. Our first class of attacks concerns the compositional approach used to construct a particular revision of EC-RAC. We invalidate the authentication and privacy claims made for that revision. We discuss the significance of the fact that RFID privacy is not compositional in general. Our second class of attacks applies to all versions of EC-RAC and reveals hitherto unknown vulnerabilities in the latest version of EC-RAC. It is a general man-in-the-middle attack executable by a weak adversary. We show a general construction for improving narrow-weak private protocols to wide-weak private protocols and indicate specific improvements for the flaws of EC-RAC exhibited in this document. Key words: RFID; attacks; privacy; authentication; compositionality;