Integration with BGP

The Whisper protocol can be integrated with BGP without changing the basic packet format of BGP. Specifically, we do not need any additional field for the Whisper signature. BGP uses community attributes within UPDATE messages that can be leveraged for embedding the signature attributes. Community attributes are $32$ bit values which are optional BGP attributes that are mainly used for community-based routing mainly for multi-homing ISPs.

This design offers us many advantages over updating a version of BGP. First, a single update message can have several community attributes and one can split a signature among multiple community attributes. Second, a community attribute can be set using the BGP configuration script to allow operators the flexibility to insert their own community attribute values. In a similar vein, one can imagine a stand-alone whisper library computing the signatures and a simple interface to insert these signatures within the community attributes. Third, one can reserve a portion of the community attribute space for whisper signatures. In today's BGP, community values can be set to any value as long as they are interpreted correctly by other routers.

Our implementation uses the following semantics for the community attribute: if the first $8$ bits of an attribute are set to $0xF0$ and $0xF1$, then the remaining $24$ bits refer to a portion of the $seed$ and $N$ attributes in the signature. An RSA based Whisper signature uses $2048$ bits per signature field - $1024$ bits for the seed and $1024$ bits for $N$. Such a signature uses $88$ community attributes. An ECC based Whisper implementation uses $512$ bits per signature and hence uses only $22$ community attributes.