Кодирование и декодирование

Question

Я хочу закодировать некоторый текст, который мог бы быть длиной в 1 charchter или или 10000 или бесконечным и декодировать (обратный алгоритм).

Я смотрю что-то вроде MD5 на PHP, но обратимо, поскольку MD5 - это один из способов.

Это может быть сервер или JavaScript. Если и то и другое, то еще лучше.

Answer 1

Для сжатия

В Javascript, http://rumkin.com/tools/compression/compress_huff.php

Также взгляните на сжатие / распаковку текста javascript

Для шифрования

В PHP вы можете использовать mcrypt:

http://www.php.net/manual/en/function.mcrypt-encrypt.php

http://www.php.net/manual/en/function.mcrypt-decrypt.php

Пример кода (с сайта выше):

<?php
class Cipher {
    private $securekey, $iv;
    function __construct($textkey) {
        $this->securekey = hash('sha256',$textkey,TRUE);
        $this->iv = mcrypt_create_iv(32);
    }
    function encrypt($input) {
        return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $this->securekey, $input, MCRYPT_MODE_ECB, $this->iv));
    }
    function decrypt($input) {
        return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $this->securekey, base64_decode($input), MCRYPT_MODE_ECB, $this->iv));
    }
}

$cipher = new Cipher('secret passphrase');

$encryptedtext = $cipher->encrypt("hide me");
echo "->encrypt = $encryptedtext<br />";

$decryptedtext = $cipher->decrypt($encryptedtext);
echo "->decrypt = $decryptedtext<br />";

var_dump($cipher);
?> 

Answer 2

Если вы хотите сжать строку, см. этот вопрос для получения информации о реализации JavaScript в LZW, Huffman, LZ77 и других. Я почти уверен, что в PHP есть похожие библиотеки.

Answer 3

import java.io.*;
class ed2
{

BufferedReader obj = new BufferedReader(new InputStreamReader(System.in));

void encode()throws InterruptedException,IOException
{
    String rs,ren;

    encoder_symbol();
    rs = encode_input();
    ren = encode_find(rs);
    encode_display(ren);
}

void decode()throws InterruptedException,IOException
{
    String rs,rde;

    decoder_symbol();
    rs = decode_input();
    rde = decode_find(rs);
    decode_display(rde);
}

void encoder_symbol()throws InterruptedException //just for fun
{
    System.out.println("********  ***         ***  *********  ************  ******      ********  *****");
    Thread.sleep(100);
    System.out.println("********  ****        ***  *********  ************  ********    ********  *** **");
    Thread.sleep(100);
    System.out.println("***       *****       ***  ***        ***      ***  ***   ***   ***       ***  **");
    Thread.sleep(100);
    System.out.println("***       *** **      ***  ***        ***      ***  ***    ***  ***       *** **");
    Thread.sleep(100);
    System.out.println("******    ***  **     ***  ***        ***      ***  ***    ***  ******    *****");
    Thread.sleep(100);
    System.out.println("******    ***   **    ***  ***        ***      ***  ***    ***  ******    *****");
    Thread.sleep(100);
    System.out.println("***       ***     **  ***  ***        ***      ***  ***    ***  ***       *** **");
    Thread.sleep(100);
    System.out.println("***       ***      ** ***  ***        ***      ***  ***   ***   ***       ***  **");
    Thread.sleep(100);
    System.out.println("*******   ***       *****  *********  ************  ********    ********  ***   **");
    Thread.sleep(100);
    System.out.println("*******   ***        ****  *********  ************  ******      ********  ***    **");
    Thread.sleep(2700);

    System.out.println();
    System.out.println();
}

void decoder_symbol()throws InterruptedException // just for fun
{
    System.out.println("******      ********  *********  ************  ******      ********  *****");
    Thread.sleep(100);
    System.out.println("********    ********  *********  ************  ********    ********  *** **");
    Thread.sleep(100);
    System.out.println("***   ***   ***       ***        ***      ***  ***   ***   ***       ***  **");
    Thread.sleep(100);
    System.out.println("***    ***  ***       ***        ***      ***  ***    ***  ***       *** **");
    Thread.sleep(100);
    System.out.println("***    ***  ******    ***        ***      ***  ***    ***  ******    *****");
    Thread.sleep(100);
    System.out.println("***    ***  ******    ***        ***      ***  ***    ***  ******    *****");
    Thread.sleep(100);
    System.out.println("***    ***  ***       ***        ***      ***  ***    ***  ***       *** **");
    Thread.sleep(100);
    System.out.println("***   ***   ***       ***        ***      ***  ***   ***   ***       ***  **");
    Thread.sleep(100);
    System.out.println("********    ********  *********  ************  ********    ********  ***   **");
    Thread.sleep(100);
    System.out.println("******      ********  *********  ************  ******      ********  ***    **");
    Thread.sleep(1000);

    System.out.println();
    System.out.println();
}

String encode_input()throws IOException
{
    String s;
    System.out.println("ENTER THE STRING TO BE ENCODED");
    s = obj.readLine();
    return(s);
}

String decode_input()throws IOException
{
    String s;
    System.out.println("ENTER THE CODE TO BE DECODED");
    s = obj.readLine();
    return(s);
}

String encode_find(String s)//converting the string into its binary equivalent
{
     int ac,i,j,l,chklen;
     String bc,en="";
     char ic;
     l = s.length();    
     for(i=0;i<l;i++)
     {   
         ic = s.charAt(i); //takes out every character
         bc = ""; 
         ac = (int)ic;  //ASCII value of this character
         while(ac!=0)
         {
             bc = Integer.toString((ac%2)) + bc; //converting the ASCII value into binary equivalent
             ac = ac/2;
         }
         chklen = bc.length();//length of the binary equivalent
         if(chklen<7)
         {
            for(j=1;j<=(7-chklen);j++) //increasing the length of binary equivalent so that it becomes equal to 7
            {  
                bc = "0" + bc;
            }
         }
         en = en+bc; //concatenating all the binary equivalent into one string
     }
     return (en);
}

String decode_find(String s)// converts binary(i.e. in the form of dots and space) to decimal
{
    int f;//for the index of every character of code
    long l,i,j,ac;
    char c;
    String de="";

    l = s.length();
    f = 0;//index of first caharcter
    for(i=0;i<(l/7);i++)//since the length of every binary equivalent of a character is 7 therefore there will be (length/7) characters in a code of length l
    {
        ac = 0;//intializes the decimal(ASCII) equivalent to zero
        for(j=6;j>=0;j--)//loop will work 7 times for every binary equivalent of a character
        {
            c = s.charAt(f);//takes out every dot or space
            if(c=='.')//it means that c corresponds to 'one'
            {
                ac = ac + ((int)Math.pow(2,j));//converting binary into decimal(ASCII) equivalent by adding all the powers of 2 which correspond to one('.') 
            }
            f++;//increasing the index for next character of binary equivalent
        }
        de = de + ((char)ac);//converts the ASCII equivalent into character and then concatenates it with the intitial string
    }
    return(de);
}

void encode_display(String en)//displays the code
{
    int i,l;
    char ic;
    System.out.println("YOUR ENCODED MESSAGE IS :");
    l=en.length();
    for(i=0;i<l;i++)
    {
        ic=en.charAt(i);
        if(ic=='1')//for every 'one' it will print '.'(dot)
        {
             System.out.print(".");
        }
        else if(ic=='0')//for every 'zero' it will print ' '(space)
        {
             System.out.print(" ");
        }
    }
}

void decode_display(String de)
{
    System.out.println(de);
}

public static void main(String args[])throws IOException,InterruptedException
{
    BufferedReader obj = new BufferedReader(new InputStreamReader(System.in));

    char ch;

    ed2 ed = new ed2();

    System.out.println("PRESS 'E' TO ENCODE A MESSAGE OR PRESS 'D' TO DECODE A MESSAGE");
    ch = (char)obj.read();

    if((ch=='e')||(ch=='E'))
    {
        ed.encode();
    }
    else if((ch=='d')||(ch=='D'))
    {
        ed.decode();
    }
}

}

Answer 4

Существуют реализации rot13 для PHP и JS , а также кодировка URL ( PHP , JS ).