Signcryption is a public key cryptographic method that achieves unforgeability and confidentiality simultaneously with significantly smaller overhead than that required by "digital signature followed by public key encryption". It does this by signing and encrypting a message in a single step. An aggregate signcryption scheme allows individual signcryption ciphertexts intended for the same recipient to be aggregated into a single (shorter) combined ciphertext without losing any of the security guarantees. In this paper, we present an unrestricted aggregate signcryption scheme in the identity-based setting using multilinear maps. To the best of my knowledge, our new scheme is the first identity-based aggregate signcryption scheme that admits unrestricted aggregation.
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