Which option would be the best choice for protecting confidential emails based on the given scenario?
The best choice for protecting confidential emails in the given scenario is option a) SendE(M,Ka),Sign(Kg,PrA).
Analysis of Option a) SendE(M,Ka),Sign(Kg,PrA)
a) SendE(M,Ka),Sign(Kg,PrA)
In this option, the email M is being encrypted using Bob's encryption public key Ka (SendE(M,Ka)) and then signed using Alice's private key for signing (Sign(Kg,PrA)). To protect confidential emails, it is important to ensure both confidentiality and integrity.
Confidentiality means that only the intended recipient can access and read the email, while integrity means that the email remains unchanged during transit. By encrypting the email using Bob's public key Ka, Alice ensures that only Bob can decrypt and read the email, providing confidentiality.
Additionally, by signing the email using Alice's private key PrA, Alice provides a digital signature that verifies the authenticity of the email and ensures that the content has not been tampered with during transit, providing integrity.
Therefore, option a) SendE(M,Ka),Sign(Kg,PrA) is the best choice for protecting confidential emails as it combines both confidentiality and integrity measures.
By using both encryption and digital signatures, the email remains confidential and tamper-proof, ensuring that the original content is unchanged and only the intended recipient can access it.