What is the role of the public key in the RSA cryptosystem?

In the RSA cryptosystem, the public key plays a crucial role in the encryption of messages. This system uses a pair of keys: a public key that can be shared openly and a private key that is kept secret by the owner. When someone wants to send an encrypted message to the key holder, they use the public key to encrypt the message. The public key is mathematically linked to the private key, allowing only the holder of the private key to decrypt messages that were encrypted with the public key.

This functionality supports the confidentiality of the communication, ensuring that only intended recipients—who possess the corresponding private key—can access the original message. Thus, the public key's primary purpose in the RSA cryptosystem is indeed to encrypt messages, enabling secure communication between parties.