The present invention provides a system and method for providing certified voice and/or multimedia mail messages in a broadband signed communication system which uses packetized digital information. Cryptography is used to authenticate a message that has been compiled from streaming voice or multimedia packets. A certificate of the originator's identity and electronic signature authenticates the message. A broadband communication system user may be provisioned for certified voice and/or multimedia mail by registering with a certified mail service provider and thereby receiving certification. The called system user's CPE electronically signs the bits in received communication packets and returns the message with an electronic signature of the called system user to the calling party, along with the system user's certificate obtained from the service provider/certifying authority during registration. The electronic signature is a cryptographic key of the called party.