Cryptography

Cryptography provides these functions : 

Confidentiality (or privacy)
characteristic of a communication which prevents eaves-dropping
Authentication
process of identifying the user accessing the system, server, or data
from shared secret to digital signature
Message Integrity
characteristic of a communication which ensures the data received is the same as the data transmitted	
digital signatures assure both that the signer actually originated the message and also that the transmitted message has not been altered

Non-repudiation
difficult/impossible to deny a correct message