Methods and apparatus for authenticating data stored in semiconductor memory cells

Abstract

A method and apparatus for authenticating data stored in semiconductor memory cells. A reference fingerprint representing trapped charges in memory cells of a semiconductor device is created. Data is written to selected cells of the semiconductor device. After the data is written, the levels of trapped charges in the selected cells is determined by performing a series of read operations using progressively greater read thresholds. The level of trapped charges in a memory cell is identified by noting the voltage threshold at which the memory cell is read as a digital “1”. Once the levels of trapped charges of the memory cells are identified, a reference fingerprint is created to identify the semiconductor device. The reference fingerprint may be stored on the semiconductor device or on an external device. When it is desired to authenticate the semiconductor device, an authentication fingerprint is created by determining levels of trapped charges in selected cells of the semiconductor device, similar to the way in which the stored reference fingerprint was created. The stored reference fingerprint is retrieved and compared to the authentication fingerprint. If the authentication fingerprint matches the stored reference fingerprint, the semiconductor device is authenticated. For additional security, an offset voltage may be added to data which is written to the selected cells of the semiconductor device, or the reference fingerprint may be encrypted before storage. Fuzzy logic techniques may be used to compensate for environmental and hardware related fluctuations in the levels of trapped charges of the memory cells.