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Citation  Proceedings of EUROCRYPT, 2003

Authors  Dan Boneh
Craig Gentry Ben Lynn Hovav Shacham 
An aggregate signature scheme is a digital signature that supports aggregation: Given n signatures on n distinct messages from n distinct users, it is possible to aggregate all these signatures into a single short signature. This signal signature (and the n original messages) will convince the verifier that the n users did indeed sign the the n original messages (i.e., user i signed message Mi for i = 1, ..., n). In this paper we introduce the concept of an aggregate signature, present security models for such signatures, and give several applications for aggregate signatures. We construct an efficient aggregate signature for a recent short signature scheme based on bilinear maps due to Boneh, Lynn, and Shacham. Aggregate signatures are useful for reducing the size of certificate chains (by aggregating all signatures in the chain) and for reducing message size in secure routing protocols such as SBGP. We also show that aggregate signatures give rise to verifiably encrypted signatures. Such signatures enable the verifier to test that a given ciphertext C is the encryption of a signature on a given message M. Verifiably encrypted signatures are used in contractsigning protocols. Finally, we show that similar ideas can be used to extend the short signature scheme to give simple ring signatures.