Biblio

This paper presents CaptchaGG, a model for recognizing linear graphical CAPTCHAs. As in the previous society, CAPTCHA is becoming more and more complex, but in some scenarios, complex CAPTCHA is not needed, and usually, linear graphical CAPTCHA can meet the corresponding functional scenarios, such as message boards of websites and registration of accounts with low security. The scheme is based on convolutional neural networks for feature extraction of CAPTCHAs, recurrent neural forests A neural network that is too complex will lead to problems such as difficulty in training and gradient disappearance, and too simple will lead to underfitting of the model. For the single problem of linear graphical CAPTCHA recognition, the model which has a simple architecture, extracting features by convolutional neural network, sequence modeling by recurrent neural network, and finally classification and recognition, can achieve an accuracy of 96% or more recognition at a lower complexity.

Proof-of-Work (PoW) is a popular protocol used in Blockchain systems to resolve double-spending problems. However, if an attacker has access to calculation hash power greater than half of the total hash power, this attacker can create a double-spending attack or 51% attack. The cost of creating a 51% attack is surprisingly low if hash power is abundantly available. That posts a great threat to lots of PoW blockchains. We propose a technique to combine history weighted information of miners with the total calculation difficulty to alleviate the 51% attack problem. Analysis indicates that with the new technique, the cost of a traditional attack is increased by two orders of magnitude.

In the vertical multi-level public network, the ciphertext video needs to support the distribution of key in the whole network when it is shared across different security domains horizontally. However, the traditional key management mode faces great pressure on the security classification and encryption efficiency, and especially, it cannot fully ensure the security of content and key when sharing across-domains. Based on the above analysis, this paper proposes a cross domain video security sharing solution based on white box encryption theory to improve the security of video data sharing. In this solution, the white box encryption technology is adopted to establish the data sharing background trust mechanism based on the key management center, and we study the white box key protection technology of the video terminal to support the mass level key distribution in the network and the online security generation and replacement of the white box password module, so that the safe and fast cross domain exchange and sharing of video data are realized.