Two friends want to exchange a confidential document by e-mail. They decide to use cryptography
to protect the confidentiality of the document. To be able to encrypt alid decrypt the document they
first exchange the key that is both used for encryption and decryption by phone.
What type of encryption system is used by the two friends?

A.
Asymmetrical system

B.
Public Key Infrastructure (PKI)

C.
Symmetrical system

Explanation: