Exercise 4
encrypt -
	- Read the symmmetric key from file (See fread(..))
	- Encrypt the symmetric key using public key encryption and write it into a file named "C1" (You can use the public_encrypt(..) function of Exercise 2)
	- Set the encryption key (See AES_set_encrypt_key())
	- Generate random IV of 16 bytes (See RAND_bytes(..) ) and write it into a file named "IV"
	- Encrypt the message using AES encryption (See AES_cfb128_encrypt(..)) 
	- While encryption, take care that you encrypt the message in chunks of AES_BLOCK_SIZE and write it into a file named "C2"


decrypt -
	- Read the cipher C1 from file (See fread(..))
	- Decrypt the C1 using private key decryption to get the symmetric key (You can use the private_decrypt(..) function of Exercise 2)
	- Set the encryption key (See AES_set_encrypt_key())
	- Read the IV from file (See fread(..))
	- Decrypt the message using AES decryption (See AES_cfb128_encrypt(..) and you may use the parameter AES_DECRYPT for decryption) 
	- While decryption, take care that you decrypt the cipher in chunks of AES_BLOCK_SIZE and write it into a file with name given in the parameter (char* decrypted_file)


General Guidance - 
	- While reading/writing a file take care that it may have special characters (like '\0', '\n' etc.) which may cause partial read/write. 
	To avoid these you may use fread() and fwrite() to read/write all the bytes.
	- Close all the files that you open
