How to Safely Send a File Over the Internet?

How can Ade securely send a file to Cindy over the Internet?

A. Encrypt the file using Ade's private key and Cindy's public key
B. Encrypt the file using Ade's public key and Cindy's private key
C. Encrypt the file using Ade's private key and then encrypt it again using Cindy's private key
D. Encrypt the file using Ade's public key and then encrypt it again using Cindy's public key

Answer:

Ade should encrypt the file using Ade's private key and Cindy's public key.

In order to safely send a file to Cindy over the Internet, Ade should follow a specific encryption process. By encrypting the file using Ade's private key and Cindy's public key, Ade can achieve both confidentiality and authenticity.

Encrypting the file using Ade's private key ensures that only Cindy, possessing Cindy's corresponding public key, can decrypt and read the file. This step guarantees confidentiality.

Additionally, by encrypting it again using Cindy's public key, Ade establishes the authenticity of the file and its origin. This ensures that the file can only be decrypted by Cindy, who holds the corresponding private key.

This double encryption process guarantees that the file remains secure during transmission over the Internet, allowing only the intended recipient to access and verify its source.