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Secured Private Key Handling using Transposition Cipher Technique

Developments in communications technology motivate most businesses and academic institutions to move towards the use of digital documents. Digital signature is an alternative way in signing a document using a pen. It is used for verifying the authenticity of digital messages or documents. A private key is required to sign a digital document. It is a vulnerable component of the public key cryptosystem. Once unauthorized user gains knowledge of the private key, a valid digital signature can be produced on behalf of the registered user. This paper proposes a transposition cipher technique to protect the private key from unauthorized users. It rearranges the sequence of private key characters. The mapping of characters’ position shifting is based on the defined Fibonacci series and created equations. This technique makes the private key unusable, thus prevent unauthorized access in case of loss or theft. The degree of security performance of the proposed technique is evaluated using the correlation coefficient cryptographic test. The correlation values determine the confusion effect of the block cipher. The results obtained from the test showed that the proposed algorithm provides a strong non-linear relationship between the plaintext and ciphertext.