The greatest concern to an IS auditor reviewing an organization’s method to transport sensitive data between offices is that the method relies exclusively on the use of asymmetric encryption algorithms. Asymmetric encryption algorithms, also known as public key encryption, use two different keys for encryption and decryption: a public key that is shared with anyone who wants to communicate with the sender, and a private key that is kept secret by the sender. Asymmetric encryption algorithms are more secure than symmetric encryption algorithms, which use the same key for both encryption and decryption, but they are also slower and more computationally intensive. Therefore, relying exclusively on asymmetric encryption algorithms may not be efficient or practical for transporting large amounts of sensitive data between offices. A better method would be to use a combination of symmetric and asymmetric encryption algorithms, such as using asymmetric encryption to exchange a symmetric key and then using symmetric encryption to encrypt and decrypt the data.
The other options are not as concerning as option C. The method relying exclusively on the use of public key infrastructure (PKI) is not a concern, because PKI is a system that provides the services and mechanisms for creating, managing, distributing, using, storing, and revoking digital certificates that are based on asymmetric encryption algorithms. PKI enables secure and authenticated communication between parties who do not have a prior trust relationship. The method relying exclusively on the use of digital signatures is not a concern, because digital signatures are a way of verifying the authenticity and integrity of a message or document by using asymmetric encryption algorithms. Digital signatures ensure that the sender cannot deny sending the message or document, and that the receiver can detect any tampering or alteration of the message or document. The method relying exclusively on the use of 128-bit encryption is not a concern, because 128-bit encryption is a level of encryption that uses a 128-bit key to encrypt and decrypt data. 128-bit encryption is considered to be strong enough to resist brute-force attacks by modern computers. References: Asymmetric vs Symmetric Encryption: What are differences?, Public Key Infrastructure (PKI), Digital Signature, What is 128-bit Encryption?
