Non-contact measurement of pulse wave velocity (PWV) using red, green, and blue (RGB) digital color images is proposed. Generally, PWV is used as the index of arteriosclerosis. In our method, changes in blood volume are calculated based on changes in the color information, and is estimated by combining multiple regression analysis (MRA) with a Monte Carlo simulation (MCS) model of the transit of light in human skin. After two pulse waves of human skins were measured using RGB cameras, and the PWV was calculated from the difference of the pulse transit time and the distance between two measurement points. The measured forehead-finger PWV (ffPWV) was on the order of m/s and became faster as the values of vital signs raised. These results demonstrated the feasibility of this method.
Double Random Phase Encoding (DRPE), which is a typical optical encryption technique, has been reported to be
vulnerable to Known Plaintext-Attacks (KPAs) using a Phase Retrieval Algorithm (PRA). But the reported case in which
the encryption key is successfully estimated was that the plain image was rather simple such as the image of a character.
In addition, although Phase Only DRPE (PO-DRPE) was proposed to achieve more resistance to the KPA than Complex
DRPE (C-DRPE) in which both amplitude and phase components are used as an encrypted image, no quantitative results
about the relationship between the vulnerability and the plaintext image. In this paper, we show the result of quantitative
analysis on KPA by PRA to C-DRPE and PO-DRPE, for the plaintext images of different characteristics. As a result of
experiment, KPA to C-DRPE succeeded to estimate the correct key while the probability of success became lower when
the number of non-zero pixel increases in the plaintext image. However, KPA to PO-DRPE enabled to estimate only
"singular" keys, which are effective for no more than given plaintext/ciphertext image pair and far different from the
correct encryption key. We also conducted KPA using two plaintext-ciphertext image pairs for KPA. In the case when
two plaintext-ciphertext image pairs were given to KPA, the cryptanalysis succeeded with higher probability than the
case of one. Moreover, the probability of success in the KPA was high even in PO-DRPE.
Fingerprint verification for smart card holders is one of the methods which are able to identify smart card holders with a high level of security. However, an ingenious implementation is needed to execute it in the embedded processor quickly and safely, because of its computational burden and the limitation of the smart card performance. For this purpose, we propose a hybrid method which is a combination of personal identification number (PIN) verification with a smart card and an optical fingerprint verification method. The result of a preliminary computer simulation to evaluate the proposed system shows that false acceptance rate is completely zero, though false rejection rate is a little inferior to the conventional figerprint verification system.