(RSA): Bob has an RSA key with modulo N in a size that should be secure, about 2048 bits an a public power of e=3 that should provide an efficient encryption.

Alice wants to send bob a big file using a symmetrical encryption: Alice randomly chooses a key k for AES encryption and sends it to bob using RSA encryption as following: and after that sends the file encrypted by AES using the key k.

In order to decrypt it, Bob first calculates and then decrypts the file using AES with k as the key. is this encryption indeed secure?

C=k modN C = hmodN