Cryptographic Randomness from Air Turbulence in Disk Drives

Abstract. A computer disk drive's motor speed varies slightly but irregularly, principally because of air turbulence inside the disk's enclosure. The unpredictability of turbulence is well-understood mathematically; it reduces not to computational complexity, but to information losses. By timing disk accesses, a program can e ciently extract at least 100 independent, unbiased bits per minute, at no hardware cost. This paper has three parts: a mathematical argument tracing our RNG's randomness to a formal de nition of turbulence's unpredictability, a novel use of the FFT as an unbiasing algorithm, and a sanity check" data analysis.

• Type: Conference
• Year: 1994
• Where: CRYPTO
• Authors: Don Davis, Ross Ihaka, Philip Fenstermacher
• Keywords: Air Turbulence, CRYPTO 1994, Cryptology, Disk Drive Motor, Turbulence's Unpredictability