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Spectral reflectance in the near‐infrared (NIR) and short‐wave–infrared (SWIR) regions shows decreasing water absorption troughs upon crop water stress. In this study, decreasing water absorption troughs were identified from reflectance of irrigated wheat crop. The crop was grown under two different irrigation methods, sprinkler and flood irrigation. Crop reflectance was measured using an ASD FieldSpec 3 (350–2,500 nm) hand‐held spectroradiometer at 1 week before the critical growth stages. Among different growth stages, wheat crop was found to be under stress in crown root initiation, jointing, and flowering. Results based on crop yield, and raw and first derivative spectral analysis indicated that flood‐irrigated wheat had more stress compared with sprinkler‐irrigated wheat. Five water stress‐sensitive wavelengths (974; 1,195; 1,455; 1,791; and 1,935 nm) were identified from flood‐irrigated wheat. Among them, two wavelengths (974 and 1,195 nm) were found to be highly water sensitive and good indicators for water stress. Detecting crop water stress prior to the critical growth stages of wheat helps in proper irrigation scheduling.

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Summary Designing an efficient, short, and secure authentication algorithm for resource‐constrained sensor nodes of wireless sensor networks (WSNs) is a challenging task. Authentication in WSNs is mainly performed by the digital signature algorithm. In this paper, we propose an efficient, short, and secure pairing computation‐free ID‐based authentication algorithm (signature scheme) ESS‐IBAA for WSNs which completely follows the rule of identity‐based cryptosystem. Identity‐based schemes, unlike traditional public‐key infrastructure (PKI)‐based schemes, remove the need for public‐key certificates for public‐key validation. It also removes extra costs associated with the public‐key certificate and traffic management. Further, due to the requirement of low power and fast authentication, bilinear pairing computation‐free identity‐based signature schemes are applicable in WSNs. Keeping this in mind, ESS‐IBAA scheme is proposed, which is pairing computation free and uses a general cryptographic hash function in the place of a costly map‐to‐point hash function. The proposed scheme ESS‐IBAA is secure against existential forgery on adaptive chosen message and ID attack in the random oracle model under the hardness of the elliptic curve discrete logarithm problem (ECDLP). Moreover, comparative performance analysis shows that the proposed scheme ESS‐IBAA is much more efficient in both communication cost and computation cost from the existing related schemes.

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