We demonstrate that unmodified commercial Flash memory can provide three important security functions: true random number generation, digital fingerprinting and information hiding. Use of random telegraph noise (a type of quantum noise source in highly scaled Flash memory cells) enables high quality true random number generation at a rate up to 10Kbits / second. A scheme based on partial programming exploits process variation in threshold voltages to allow quick generation of unique fingerprints that can be used for identification and authentication. Aging-induced biases can hide data within the analog characteristic of Flash as the program time of individual bits. Because the technique uses inherent behavior, normal Flash memory operations are not affected and hidden information is invisible in the data stored in the memory. Even if an attacker checks a Flash chip's analog characteristics, experimental results indicate that the hidden information is difficult to distinguish from inherent manufacturing variation or normal wear on the device. Moreover, the hidden data can survive erasure of the Flash memory data. All schemes require no change to Flash chips or interfaces, and do not require additional hardware.