Systems and methods for call authentication are provided. A method can include an enrollment protocol that ensures users control the number they claim to own, a handshake protocol that mutually authenticates the calling parties, and a call integrity protocol that ensures the security of the voice channel and the content it carries. A server can act as either an endpoint or intermediary between user clients and client-server architecture can be employed. All protocols can include end-to-end cryptography and the enrollment protocol can issue a certificate that binds the identity of the client to a phone number.