Differential cryptanalysis of a medical image cryptosystem with multiple rounds.

Area of Science:

• Cryptography
• Medical Imaging
• Information Security

Background:

• A recent chaos-based medical image encryption scheme with permutation-substitution architecture was proposed.
• The original scheme claims high security with few rounds due to bit-level cat map shuffling.

Purpose of the Study:

• To analyze the security of the proposed chaos-based medical image encryption scheme.
• To identify and exploit vulnerabilities in the encryption scheme.

Main Methods:

• Differential cryptanalysis was employed to assess the scheme's resistance to attacks.
• A novel method, double differential cryptanalysis comparison (DDCC), was developed for multi-round analysis.
• The analysis focused on key dependency and the number of chosen plain-images required for attacks.

Main Results:

• The scheme is vulnerable to differential cryptanalysis, with security depending solely on the permutation key.
• Key recovery is possible for 1-round and 2-round encryption using only 17 chosen plain-images.
• The proposed DDCC method can break multi-round encryption with 16N(2)+1 chosen plain-images.

Conclusions:

• The analyzed chaos-based medical image encryption scheme is insecure.
• The permutation-substitution architecture and bit-level shuffling do not guarantee high security against differential attacks.
• The findings highlight critical weaknesses in the cryptosystem, necessitating further research into secure medical image encryption.