Aiming at the problem that the audio steganography has low utilization of carriers, poor imperceptibility and small embedding capacity, an adaptive audio steganography based on the wavelet packet decomposition and matrix code was proposed. Comparing the differences between the wavelet-packet decomposed coefficients before and after the audio's MP3 compression, the algorithm took the unchanged bits' position of wavelet-packet decomposed coefficients as embedding carriers, which effectively increased the embedding capability. And the algorithm improved the matrix code by using chaotic model to generate random triple-groups, which promoted the safety and efficiency. As for capacity, the proposed algorithm promoted about 30%, compared with the algorithm that directly uses the medium-frequency sub-bands as the carriers. On the aspect of Signal-to-Noise Ratio (SNR), the proposed algorithm promoted about 9%, compared with the matrix steganography that fixes the triple-groups. The experimental results show that the algorithm is correct and can basically satisfies large-capacity and secure communications.

In traditional Proxy Re-Encryption (PRE), a proxy is too powerful as it has the ability to re-encrypt all delegator's ciphertexts to delegatee once the re-encryption key is obtained; And for more than one delegatees, delegator needs to generate different re-encryption key for different delegatee, which wastes a lot of resources in the calculation process. To solve these problems, an identity-based conditional proxy broadcast re-encryption was introduced. The delegator generated a re-encryption key for some specified condition during the encryption, like that the re-encryption authority of the proxy was restricted to that condition only. Moreover, the delegator's ciphertexts could be re-broadcasted to ensure the important communication and save a lot of computation and communication cost. Finally, the theoretical analysis verified the security of the scheme.