Social media blockchain is emerging as a promising solution to deal with privacy issues, by putting user privacy in edge nodes rather than centralized nodes. Under the protection of information encryption, only those who have cryptographic keys can get access to key information. This work aims at multimedia information in social media blockchain and utilizes the RSA encryption mechanism to construct the information encryption system. Due to the resilience of biometric features, the biometric cryptographic keys are not easy to be fabricated. Thus, this paper proposes a biometric keys-enhanced multimedia encryption algorithm for social media blockchain. First of all, the wiener filter is adopted to make some preprocessing operations to images, such as noise reduction. On this basis, the discrete wavelet transform is adopted to extract feature representation from images, and nonlinear approximation of contourlet transform is adopted to make feature fusion. Next, cryptographic keys can be generated from the fused biometric feature vectors to encrypt biometric data. Finally, some simulation experiments are conducted to evaluate performance of the proposal from three aspects: key generation time, security level and encryption-decryption time complexity. For key generation time, processing speed of the proposal is approximately 1–2$$ms per sample. For security level, the proposal can reach an index value beyond 95% which is higher than comparison methods. For encryption-decryption time complexity, the proposal is about 30% lower than comparison methods.

社交媒体区块链正在成为解决隐私问题的一种有前景的解决方案，它将用户隐私置于边缘节点而不是集中节点。在信息加密的保护下，只有拥有密钥的人才能访问关键信息。本工作针对社交媒体区块链中的多媒体信息，利用RSA加密机制构建信息加密系统。由于生物特征的弹性，生物特征密钥不容易被伪造。因此，本文提出了一种用于社交媒体区块链的生物识别密钥增强多媒体加密算法。首先采用维纳滤波器对图像进行一些预处理操作，如降噪等。在此基础上，采用离散小波变换从图像中提取特征表示，并采用轮廓波变换的非线性逼近进行特征融合。接下来，可以从融合的生物特征向量生成加密密钥以加密生物特征数据。最后，进行了一些模拟实验，从密钥生成时间、安全级别和加解密时间复杂度三个方面评估了该方案的性能。对于密钥生成时间，提案的处理速度约为 1-2$$每个样本的毫秒数。对于安全级别，该方案可以达到95%以上的指标值，高于对比方法。对于加密-解密时间复杂度，该提案比对比方法低约 30%。