Abstract: In this paper,a high-speed and low-power Truly Random Number Generator (TRNG) is proposed,which is based on an oscillator-sampling architecture.Its randomness is extracted from jitter in Ring Osillators.Four Ring Oscillators of relatively prime length constitute the Entropy Source.XOR operation on the four outputs of the Oscillators improves the randomness,which is also proved mathematically.The output sequences are corrected by the Von Neumann Corrector so as to eliminate the bias between bits completely.Meanwhile,an elaborate diffusion function which diffuse the output sequences is designed to further improve the randomness and distribution.Test result shows that the output sequences of the TRNG pass all the tests of Diehard and NIST SP 800-22,and the bit rate could be as high as 20Mb/s.The TRNG has been fabricated in a 0.18μm CMOS process,and utilized 0.0135mm² of die area.Power consumption is only 0.75 mW with a supply voltage of 3.3V.Hence,it's very suitable for applications in on-chip high-speed cryptography system.