Abstract: A system and method are provided for generating Unique Digital Signatures (UDS) for semiconductor memories to improve data security. Generally, the method involves allocating a number of native memory cells in a memory device; obtaining a multibit binary entropy string (BES) using variations of threshold voltages (VT) of the allocated cells as an entropy source; and mathematically manipulating the BES to generate the UDS. Optionally, the BES can be concatenated with another multibit binary number from a second entropy source internal or external to the memory device, and the result of the concatenation mathematically manipulated to generate the UDS. In one embodiment, a reference voltage is located at a median VT for the cells, and the BES is obtained by reading the cells versus the reference, assigning those having a VT above the reference a first bit value, and the remaining cells a second bit value.