in the N-Z range, the ciphertext is equal to the plaintext ASCII code value plus
19; in the a-m range, the ciphertext is equal to the plaintext
ASCII code value minus 19; in the n-z range, the ciphertext is equal to the plaintext ASCII code value minus 45.
The second class of transformation: if the plaintext is Arabic numbers, in the 0-4 range, the ciphertext is equal to plaintext multiplied by 2 plus 1; in the 5-9 range, the ciphertext is equal to plaintext multiplied by 2 minus 10.
The third class of transformation: if the plaintext is other special characters, the ciphertext is the same as the plaintext.
Take the string "Hisense $ 2011" for example, after the above steps, the ciphertext string is "uVFRAFR $ 5133".