If a wireless sensor network (WSN) is integrated
into the Internet as a part of the Internet of things (IoT), there
will appear new security challenges, such as setup of a secure
channel between a sensor node and an Internet host. In this
paper, we propose a heterogeneous online and offline signcryption
scheme to secure communication between a sensor node and an
Internet host. We prove that this scheme is indistinguishable
against adaptive chosen ciphertext attacks under the bilinear
Diffie-Hellman inversion problem and existential unforgeability
against adaptive chosen messages attacks under the q-strong
Diffie-Hellman problem in the random oracle model. Our scheme
has the following advantages. First, it achieves confidentiality,
integrity, authentication, and non-repudiation in a logical single
step. Second, it allows a sensor node in an identity-based
cryptography to send a message to an Internet host in a public key
infrastructure. Third, it splits the signcryption into two phases:
i) offline phase; and ii) online phase. In the offline phase, most
heavy computations are done without the knowledge of a message.
In the online phase, only light computations are done when a
message is available. Our scheme is very suitable to provide
security solution for integrating WSN into the IoT.