Nowadays, Internet of things (IoT) become more and more popular. At the same time, the requirements of security mechanism for multimedia in IoT received a huge concern. Multimedia data is easily shared by devises, applications and social networks set by IoT. Therefore, it is indispensable to guarantee the privacy and security of shared multimedia data. In this paper, we address the secure multimedia data sharing problem in cloud computing by designing proxy re-encryption (PRE) scheme. Our schemes cope with the issues of data validity, data confidentiality and authentication during encrypted multimedia data sharing. Unlike as usually done in the literature, we present a CCA-secure PRE scheme which removes pairings firstly. Then we design a refined CCA-secure PRE scheme called publicly verifiable PRE without parings. It is demonstrated that our schemes meet not only the security and high efficiency requirements of multimedia data sharing, but also the public verifiability. The validity of ciphertext, both the original and re-encrypted ciphertext, can be publicly verified which brings additional efficiency due to offloading the validity check of ciphertexts from the power-limited clients to any semi-honest public cloud.