A Cryptosystem of Low Key Authentic Degree

This paper analyzes the meaning and significance of key authentic degree of cryptosystem under the threat of the rubber-hose attack and ciphertext only attack. A novel cryptosystem of low key authentic degree is designed. The inner encryption is an extension like multiple-choice questions with keywords similar and contrary to the keywords in the plaintext. The corresponding decryption is like doing multiple-choice questions and the answers are decided by key. It is easy to find pseudokeys of the cryptosystem that can confuse and mislead cryptanalysts.