Özet:

In this study, the cryptanalysis of a chaos based random number generator(RNG) which is used for encryption of vein images is presented. This RNG based on a nonlinear system is deployed in a cryptographic system which is used for encryption and secure storage of dorsal hand images taken by an infrared camera. In this study, an attack method which exploits the security weaknesses of the chaos based RNG is propose. Assuming that one of the chaotic state variables of the RNG is observable and the structure of the target RNG is known, identical output bit stream of the target RNG is generated by a clone RNG used in master–slave synchronization scheme. The performance of the attack method is demonstrated using numerical simulation results. Using the attack method described in this study, it is demonstrated that it is possible to obtain the key values used for encryption of the vain images and use these key values to decrypt the images. In this study, a specific continuous-time chaos-based RNG is subjected to a cryptanalysis study to reveal the security weaknesses. However, the cryptanalysis method explained in this study can be used in the cryptanalysis of any continuous-time or discrete-time chaos-based RNGs. Therefore, this study brings light to the security weaknesses associated with chaos based RNGs and underlines the fact that chaos should not be treated as the sole entropy source in a RNG application as chaos is a deterministic phenomenon.

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