[01] Piyali Sharma, Department of Computer Science and Engineering, ICFAI (Institute of Chartered Financial Analysts of India) University, Raipur (Chhattisgarh), India. [02] Pramay Bhatpahri, Department of Mechanical Engineering, ICFAI (Institute of Chartered Financial Analysts of India University), Raipur (Chhattisgarh), India. [03] Ravi Shrivastava, Department of Physics, ICFAI (Institute of Chartered Financial Analysts of India University), Raipur (Chhattisgarh), India.

In this paper, the encryption of Hindi plaintext using the modified affine cipher technique is reported. The numerical equivalents of the characters of Hindi were retrieved in Matlab 2016. Using Hindi characters for encryption, increases the level of security of the substitution cipher because of the availability of more characters for encryption in comparison to English. According to a cryptanalyst, any substitution cipher can be broken easily specially using the frequency analysis therefore it is proposed to divide the plaintext in small groups and then assigned different keys to different section of the text. In current work the plain text is divided into the number of groups of four characters and each group is assigned with a pair of co-prime numbers. Hence, total 8 keys will be required to encrypt a plain text of length 16 characters. By doing this, a specific plaintext character can be encrypted in different characters therefore the possibility of decrypting the message by frequency is very less. Here symmetric key cryptography is used hence only the sender and receiver know the security key i.e. they share the same key. It can be predicted that, if we encrypt Hindi plaintext message using above mentioned process, then it is impossible to decrypt the encrypted message without knowing security keys.

Affine Cipher, Text Encryption, Hindi Encryption

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