In this paper, we present a scalable and secure protocol for key revocation in Wireless Sensor Networks. The protocol guarantees an authenticated distribution of new keys that is efficient in terms of storage, communication and computing overhead. The proposed protocol reduces the number and the size of rekeying messages. It achieves the necessary level of confidentiality and authenticity of rekeying messages by only using symmetric ciphers and one-way functions. Hence, the protocol results scalable, and particularly attractive for large and/or highly dynamic groups.