Various schemes have been proposed to achieve strong authentication of streamed data in a lossy network by means of "light" digital signatures. Such techniques perform a strong authentication on only one packet, to which others are linked by means of hash functions, so that the authentication property propagates to them too. Most of these schemes make the basic assumption that the signature packet is not lost, even if no practical and precise solutions are proposed that guarantee such a property. In this paper we show how adoption of some redundancy techniques can be used in the context of multicast stream authentication in order to increase probability that the signature packets are received and correctly verified against their digital signature. Finally some experimental results are presented comparing computational overheads due to the authentication schemes both at the sender and at the receiver.