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help with Caesar cipher ,thx thx thx(urgent)

beetle17beetle17 Posts: 2Member
[b][red]This message was edited by beetle17 at 2006-11-20 8:31:30[/red][/b][hr]
[b][red]This message was edited by beetle17 at 2006-11-20 8:24:43[/red][/b][hr]
l just learn C program not long time ago,it is too diffcult for me to write a cipher

(Plaintext : a nice day)
(Key : -3)
(Ciphertext : X kfZb aXv)

Cipher will accept commands from the user and perform the operations required by the commands. There are three different commands. Key command starts with "K1:"followed by a string as the key. Encryption command starts with "E1:" followed by the plaintext. Decryption command starts with "D1:" followed by the ciphertext to be decrypted. After the user inputs an encryption (or decryption) command, Cipher1 should encrypt the plaintext (or decrypt the ciphertext) using the key input by a previous key command, and print the results. The error message "key not found" should be printed if the user inputs an encryption or decryption command before a key command. If the user
inputs multiple keys, the latest key will be used in the following encryption/decryption operations. Below are two examples (underlined text is the input from the user, and italic text is the output of Cipher).
When the plaintext/ciphertext includes non-letter symbols, Cipher1 will ignore them.For example, a plaintext of "No. 2" is equivalent to "No".

Example I of Cipher:
K 1: 3
E 1: I like dogs
C i p h e r t e x t is < L olnh grjv >
D 1: L olnh grjv
P l a i n t e x t i s < I like dogs >
E 1: H e l l o
C i p h e r t e x t i s < Khoor >

Example II of Cipher:
E 1: I like dogs
K e y not found
K 1: -54
E 1: Hello
C i p h e r t e x t is < Fcjjm>
K 1: h h h h
Invalid K e y






Comments

  • beetle17beetle17 Posts: 2Member
    [b][red]This message was edited by beetle17 at 2006-11-20 23:38:22[/red][/b][hr]

    l am typeing a program about cipher ,
    to make the result:
    Example I of Cipher:
    input K 1: 3
    //P l a i n t e x t  i s < I  l i k e  d o g s >
    input E 1: I  l i k e  d o g s
    //Ciphertext is < L  o l n h  g r j v >
    output D 1: L o l n h g r j v
    input K 1: h h h h
    putput Invalid  K e y

    where K1: , D1: ,E1: are 3 different command,
    Key command starts with "K1:"followed by a string as the key.
    Encryption command starts with "E1:" followed by the plaintext.
    Decryption command starts with "D1:" followed by the ciphertext to be decrypted.

    l want to ask how could l write to separate K1: , D1: ,E1:from the input string,to let make appling different function on different command.

    l only write
    #include
    #include
    main()
    {
    char sen[100], x[100],k[100];command[]={'sen[0]','sen[1]','sen[2]',''}
    int i, key;
    gets(sen);
    switch(command[]){
    case "K1:":
    function A;
    case "D1:":
    function B;
    case "E1:":
    function C;
    default:
    printf(input error)
    }
    is it Ok?


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