In this work, a cubic spline curve is considered for Asymmetric mode encrypting data. A steady state, one dimensional equation is integrated over a control volume. The derivatives of above equation form piece wise linear profile, which leads to discretization equation with corresponding weights. These weights are initially solved to generate global variables. Those global variables are used to calculate public key which in turn use the ElGamal mode of encryption. The proposed algorithm supports the features like Authenticity of users, Security & Confidentiality of data transmitted. Going by the construction of the algorithm, Encryption is being done on blocks of data for which it consumes less computing resources. Going by complexity of the algorithm, the key length needed is about 120 bit length to provide sufficient strengths against cryptanalysis.