The message to be encrypted is stored in plaintext. Given a key k, the encryption method works as follows. First convert the letters in plaintext to integer codes in plaincode according to the following rule: _ = 0, a = 1, b = 2, ..., z = 26, and . = 27. Next, convert each code in plaincode to an encrypted code in ciphercode according to the following formula: for all i from 0 to n - 1-The message to be encrypted is stored in plaintext. Given a key k, the encryption method works as follows. First convert the letters in plaintext to integer codes in plaincode according to the following rule:　_　= 0,　a　= 1,　b　= 2, ...,　z　= 26, and　.　= 27. Next, convert each code in plaincode to an encrypted code in ciphercode according to the following formula: for all i from 0 to n- 1