PurposeDespite the growing unforeseen and catastrophic events that disrupt business operations, empirical studies on the impact of operational disruption (OD) on small and medium enterprises' (SMEs) performance dimensions are limited. The study aims to investigate the moderating effect of disruption orientation (DO) and government support (GS) on the relationship between coronavirus disease (COVID-19) OD and SMEs' performance.Design/methodology/approachQuantitative survey method was used to collect data from 170 SMEs in Nigeria, through hand-delivery questionnaires. Partial least square (PLS) structural equation modeling (SEM) was employed to analyze the data.FindingsThe result shows no significant relationship between COVID-19 OD, DO and GS with SMEs' financial performance (FP). However, the relationship between COVID-19 OD and non-financial performance (NFP) is negatively significant. The relationship between DO and NFP is positively significant. DO and GS have insignificant relationship with FP. Finally, DO and GS does not moderate any of the relationships between COVID-19 OD and the dimensions of SMEs' performance.Practical implicationsThe result implies that health-related disruptions such as COVID-19 affect only the NFP of SMEs. However, supply chain managers and SMEs are encouraged to adopt DO to enhance NFP of firms.Originality/valueThe current study is the first to evaluate the impact of health-related disruptions on the two major dimensions of SMEs' performance (FP and NFP) by incorporating the moderating role of internal (DO) and external (GS) factors in to a single framework. However, the paper revealed new theoretical and practical knowledge by illuminating the absence of significant relationship between COVID-19 OD and SMEs' FP, implying that COVID-19 disruption does not significantly affect SMEs' FP.

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Abstract:The Hill cipher is resistant to brute-force and statistical attacks, but it can be broken with a known plaintext-ciphertext attack (KPCA). In this paper, we propose a modification of the Hill cipher, HCM-PRE, which is still resistant to brute-force and statistical attacks, and is resistant also to KPCA due to dynamic encryption key matrix generating. With the modification, the new HCM-PRE can be applied widely in the systems which need high security (e.g., image encryption). Experimental results show that the proposed modification is significantly more effective in the encryption quality of images than original Hill cipher and its known modifications (HCM-PT, HCM-H, HCM-HMAC, and HCM-EE) in the case of images with large single colour areas, and slightly more effective otherwise. HCM-PRE is about two times faster than HCM-EE and HCM-HMAC and four times faster than HCM-H in the frame of our experiments.

Secure Hill cipher (SHC) modification based on dynamically changing generalized permutation matrix, SHC-GPM is proposed. It provides better security than that of SHC due to the significantly larger number of non-repeatedly generated keys ( 48 2 times greater for the parameters used in the conducted experiments). SHC-GPM is shown to be robust against the brute-force, statistical attacks, and is resistant also to known plaintext ciphertext attack (KPCA) due to dynamic encryption key matrix generating. The proposed modification is applied for colour images encryption. Experimental results show that the proposed modification is significantly more effective in the encryption quality of bitmap images than SHC in the case of images with large single colour areas and slightly more effective otherwise.