Ryoichi Sato
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Ryoichi Sato has a total of 6 co-authors. Here are the top co-authors by number of shared publications:
- Yasuyuki Nogami
Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
4 shared publications - Yuta Kodera
Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
4 shared publications - Arshad Ali
Faculty of CSE, Hajee Mohammad Danesh Science and Technology University, Dinajpur 5200, Bangladesh
3 shared publications - Takuya Kusaka
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
2 shared publications - Mitsuki Fujiwara
Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
1 shared publication - Robert H. Morelos-Zaragoza
College of Engineering, San Jose State University, San Jose, CA 95192, USA
1 shared publication
Latest Publications
- Open Access
- 21 January 2026
- Published by Association for Computing Machinery (ACM)
- p. 271-280
Lightweight IoT Security Framework Using ECC over Extension Fields with CVMA-Based Arithmetic and Pseudorandom Stream Cipher
- 21 January 2026
- Published by Association for Computing Machinery (ACM)
- p. 271-280
Open AccessLightweight IoT Security Framework Using ECC over Extension Fields with CVMA-Based Arithmetic and Pseudorandom Stream Cipher
- Open Access
Evaluation of TRNG Bit Distribution via Stable Entropy Source Synchronization on FPGA
This study examined the correlation between the number of delay flip-flops (D-FFs) connected after each ring oscillator (RO) and the bit distribution of random number sequences in an RO-based random number generator (RNG). In our previous research, unstable input signals to the XOR gate contributed to differences in bit distribution. Based on these results, we simulated how combining signals with biased distributions through XOR gates affects the overall bit distribution. Beyond this, we also conducted simulations where the inputs to the XOR gate included not just {0, 1} signals, but also three-state signals incorporating metastable states. We then proposed using multi-D-FFs as synchronization circuits for RO signals and performed analyses on RO-based RNG implementations by estimating metastable output conditions and conducting NIST Special Publication 800-22 tests regarding bit distributions. These results confirm that inserting two or more D-FFs after RO signals improves the bit distribution of RO-based RNG implementations.
Open AccessEvaluation of TRNG Bit Distribution via Stable Entropy Source Synchronization on FPGA
This study examined the correlation between the number of delay flip-flops (D-FFs) connected after each ring oscillator (RO) and the bit distribution of random number sequences in an RO-based random number generator (RNG). In our previous research, unstable input signals to the XOR gate contributed to differences in bit distribution. Based on these results, we simulated how combining signals with biased distributions through XOR gates affects the overall bit distribution. Beyond this, we also conducted simulations where the inputs to the XOR gate included not just {0, 1} signals, but also three-state signals incorporating metastable states. We then proposed using multi-D-FFs as synchronization circuits for RO signals and performed analyses on RO-based RNG implementations by estimating metastable output conditions and conducting NIST Special Publication 800-22 tests regarding bit distributions. These results confirm that inserting two or more D-FFs after RO signals improves the bit distribution of RO-based RNG implementations.
- Open Access
Transition Probability Test for an RO-Based Generator and the Relevance between the Randomness and the Number of ROs
A ring oscillator is a well-known circuit used for generating random numbers, and interested readers can find many research results concerning the evaluation of the randomness with a packaged test suit. However, the authors think there is room for evaluating the unpredictability of a sequence from another viewpoint. In this paper, the authors focus on Wold’s RO-based generator and propose a statistical test to numerically evaluate the randomness of the RO-based generator. The test adopts the state transition probabilities in a Markov process and is designed to check the uniformity of the probabilities based on hypothesis testing. As a result, it is found that the RO-based generator yields a biased output from the viewpoint of the transition probability if the number of ROs is small. More precisely, the transitions and happen frequently when the number l of ROs is less than or equal to 10. In this sense, is recommended for use in any application, though a packaged test suit is passed. Thus, the authors believe that the proposed test contributes to evaluating the unpredictability of a sequence when used together with available statistical test suits, such as NIST SP800-22.Open AccessTransition Probability Test for an RO-Based Generator and the Relevance between the Randomness and the Number of ROs
A ring oscillator is a well-known circuit used for generating random numbers, and interested readers can find many research results concerning the evaluation of the randomness with a packaged test suit. However, the authors think there is room for evaluating the unpredictability of a sequence from another viewpoint. In this paper, the authors focus on Wold’s RO-based generator and propose a statistical test to numerically evaluate the randomness of the RO-based generator. The test adopts the state transition probabilities in a Markov process and is designed to check the uniformity of the probabilities based on hypothesis testing. As a result, it is found that the RO-based generator yields a biased output from the viewpoint of the transition probability if the number of ROs is small. More precisely, the transitions and happen frequently when the number l of ROs is less than or equal to 10. In this sense, is recommended for use in any application, though a packaged test suit is passed. Thus, the authors believe that the proposed test contributes to evaluating the unpredictability of a sequence when used together with available statistical test suits, such as NIST SP800-22. - Open Access
Consideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators
A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits.
Open AccessConsideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators
A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits.