A method is provided of authenticating a digitally signed message. A chain of messages is generated. A Winternitz pair of keys is generated for each respective message. A sequence number is assigned to each of the messages. Each of the sequence numbers cooperatively identify an order of Winternitz verifiers assigned to each of the messages. A signature to a first message in the chain of messages is signed using a digital signature algorithm private key. Signatures to each of the following messages in the chain of messages are signed using both Winternitz private keys and digital signature algorithm private keys. The signed messages are broadcast from a sender to a receiver. The first signed broadcast message is authenticated at the receiver by verifying the digital signature algorithm signature. At least some of the following signed broadcast messages are authenticated at the receiver by verifying only the Winternitz signature.