A Mobile Ad-hoc Network (MANET) is a collection of wireless nodes that can dynamically form a network to exchange information without using any pre-existing fixed network infrastructure. Such networks are more vulnerable to security attacks than conventional wired networks, and hence cryptographic schemes are usually used to ensure security for them. It is worth noting that the nodes in MANETs are with low computational power and communicate over relatively bandwidth constrained wireless links, and thus the deployed cryptographic schemes should usually be highly efficient in term of both computational cost and communication overhead. To ensure the data confidentiality for MANETs, in this paper, we present a new hierarchical identity-based encryption (HIBE) scheme, which enjoys the advantages of low computational cost and light communication overhead. We further propose a new hierarchical identity-based key encapsulation mechanism (HIBKEM) based on our HIBE scheme. The proposed HIBKEM scheme is fully secure against adaptive chosen-ciphertext attack, and has a tight security reduction in the standard model.