What is the main purpose of using public key encryption?

The main purpose of using public key encryption is to allow secure sharing of encryption keys. This method leverages a pair of keys: a public key, which can be shared openly, and a private key, which is kept secret by the owner. When someone wants to send a secure message, they encrypt it using the recipient's public key. Only the recipient, who possesses the corresponding private key, can decrypt and read the message. This mechanism ensures both confidentiality and security in the exchange of sensitive information, making it safe for individuals to share keys over potentially insecure channels.

In contrast, the other options do not align with the primary function of public key encryption. While public key encryption can indirectly aid in data transmission security, it is not primarily designed to speed up data transfer or to enhance data compression. Additionally, it does not focus on data redundancy, which involves creating copies of data to prevent loss. Instead, the cornerstone of public key encryption is its ability to facilitate safe key exchange to enable secure communications.