A compact, durable, low-reagent-usage, portable miniaturized electrochemical sensor is successfully developed for the high sensitivity detection of trace lead. We fabricated micropillars array working electrodes on the chip and established ultra-low concentration sodium acetate-acetate (NaAC-HAC) buffers (pH ≈ 4.5) system to enhance the detection sensitivity of the sensor. The ultra-low concentration buffer possesses unique features such as low baseline current and high peak current difference height. The analytical performance of the fabricated electrochemical sensor with 3D gold (Au) working electrodes modified by bismuth-film was comprehensively studied. The microsensor exhibited a high sensitivity of 0.0412 µA ppb −1 and a satisfactory detection limit of 0.15 ppb when detecting lead ions under optimized conditions. Moreover, good linearity (correlation coefficient: 0.9993) with lead ion measurements in the concentration range of 1-120 ppb and excellent repeatability (RSD: 1.79%) was obtained, the chip has satisfactory selectivity for common interference ion. Besides, a low consumption of 350 µl of reagents per test was acquired. Finally, the proposed microsensor was applied to detect trace metal ions in tap and lake samples with satisfactory results.

For the characteristics that the signing speed must be quick and the system must be simply deployed in the digital signature system of office automation, a method of digital signature with encryption based on combined symmetric key, symmetric technology and hardware technology is proposed. This method stores key seed matrix, symmetric key algorithm and combined symmetric key algorithm in hardware equipment, in additional to, hardware equipment has the functions of creating symmetric key by combined key seed matrix with combined symmetric key algorithm and digital signature. The advantages of the proposed method is that the key is one-time and timevariant and the key update and maintenance is automation so the key is maintenance-free; Compared with traditional Asymmetric digital signature algorithms, this method has the superiority of fast deciphering and simple key management.

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