Design of a Novel TRNG Based on MSFRO and STR Entropy Source

True random numbers are used as keys because of their unpredictability, and True Random Number Generator (TRNG) is also part of the encryption system. In this paper, a new TRNG is designed, which uses Multi-Stage Feedback Ring Oscillator (MSFRO) and Self-Timing Ring (STR) as the mixed entropy source of TRNG. Among them, MSFRO improves randomness by increasing the feedback loops in the oscillator and using output results to control the number of feedback loops as well as increasing the clock jitter range and sampling frequency. The entropy source is sampled by the clock after frequency division, and then the optimized von Neumann verifier and lfsr after metastable elimination, so as to eliminate the correlation of the data and improve the randomness. In addition, AES encryption algorithm is also added to promote the randomness of generating random numbers to improve security. The TRNG is implemented on a DE2-115 FPGA board, and the generated bitstream under a clock operating at 50MHz successfully pass the 15 items of the NIST SP800-22 test. The randomness and independence of the entropy source are verified, which highlights its great potential for hardware security and performance.