Cloud computing is a developing, very buoyant and nascent paradigm offering numerous solutions to the mirage of challenges and troubles confronting the IT world. It is an online computing solution for on-demand scaling, sharing and abstraction of unlimited resources. Since the significance of trust and confidence in cloud data or information transmission cannot be underestimated, it is obligatory that adequate mechanism be put in place to guarantee the safety of data provided on a Card-Not-Present (CNP) transaction mode. On this note, this paper presents an RSA algorithm with encryption and decryption-based solution to the problems of data confidentiality and integrity. While the encryption mechanism provides secured and safe representation of financial data (such as credit card details) on the cloud, a message digest mechanism is used to decrypt the encrypted files at the gateway as well as generate and send a digest message for the transaction instrument to the user for authentication. Decryption by unauthorized user is effectively checked because the security key is exclusive to data owner and financial data is not domiciled on the merchant network. Experimental study and online survey of the system reveal its very high ratings for guaranteeing data safety and confidentiality as well as the efficacy of the digital signature, the RSA modulus and security keys (public and private) for reliable and attack-proof transactions.