Symmetric account authentication

A method for symmetric authentication is provided. This method includes generating a first challenge message containing a first string; encrypting the first challenge message; transmitting the encrypted first challenge message to a second device; receiving a first answer message from the second device; decrypting the first answer message; and authenticating the second device based on determining the decrypted first answer message contains the first string. Upon successful authentication of the second device, the method further includes receiving an encrypted second challenge message from the second device; decrypting the encrypted second challenge message; generating a second answer message containing a second string; encrypting the second answer message; and transmitting the encrypted second answer message to the second device.