Advancement of True Random Number Generators Based on Sound Cards Through Utilization of a New Post-processing Method

Quality of true random number generators (TRNGs) based on a sound card depends of two components: an "unpredictable" source with high entropy, and a post processing function which, when used on a digitalized form of a random signal source, produces a result that is statistically very close to the uniform distribution. This paper presents a method of obtaining true random bits using hardware of a computer sound card, on whose audio input through the use of a microphone a random environmental noise signal is brought and for post-processing a new procedure of distributing bits is used or so called "Mixing Bits in Steps and XORing of Adjacent Bits" (MiBiS&XOR). With the presented distillation procedure, in a simple and efficient way, adjacent input bits, who are in a certain correlation, are separated and divided one from another, by which reduces the total autocorrelation and then in this new sequence, adjacent bits are XORed which increases the entropy and reduces bias of output bit sequence. Experimental statistical randomness tests performed on sequences of bits obtained as a result of the proposed method, confirm the excellent quality of the TRNGs output.