Python implements a simple example of a reversible cryptographic program

This article illustrates a simple reversible encryption program implemented in Python. Share with you for your reference. The details are as follows:

The Python code is as follows:

#coding=utf-8   

'''''  

    Description:  Reversible encryption and decryption   

    Environment: python2.5.x  

    Author:idehong@gmail.com  

''' 

import os   

import sys   

class Code(object):   

    ''''' Reversible encryption and decryption ''' 

    def __init__(self, key = "idehong@gmail.com"):   

        self.__src_key = key   

        self.__key = self.__get_strascii(self.__src_key, True)   

    def encode(self, value):   

        ''''' Encryption function ,  Encrypted into a string of Numbers ''' 

        return  "%d" % (self.__get_strascii(value, True) ^ self.__key)   

    def decode(self, pwd):   

        ''''' Decryption function ''' 

        if self.is_number(pwd):   

            return self.__get_strascii( (int(pwd)) ^ self.__key, False )   

        else:   

            print 'require number.' 

    def reset_key(self, key):   

        ''''' To reset key''' 

        self.__src_key = key   

        self.__key = self.__get_strascii(self.__src_key, True)   

#===============================================================================   

#         Internal call interface    

#===============================================================================   

    def __get_strascii(self, value, bFlag):   

        if bFlag:   

            return self.__get_str2ascii(value)    

        else:   

            return self.__get_ascii2str(value)   

    def __get_str2ascii(self, value):   

        ls = []   

        for i in value:   

            ls.append( self.__get_char2ascii( i ) )   

        return long("".join(ls))   

    def __get_char2ascii(self, char):   

        ''''' Gets a single character acsii Code value ''' 

        try:   

            return "%03.d" % ord(char)   

        except (TypeError, ValueError):   

            print "key error." 

            exit(1)   

    def __get_ascii2char(self, ascii):   

        if self.is_ascii_range(ascii):   

            return chr(ascii)   

        else:   

            print "ascii error(%d)" % ascii   

            exit(1)          

    def __get_ascii2str(self, n_chars):   

        ls = []   

        s = "%s" % n_chars   

        n, p = divmod(len(s), 3)   

        if p > 0:   

            nRet = int(s[0 : p])   

            ls.append( self.__get_ascii2char(nRet))   

        pTmp = p   

        while pTmp < len(s):   

            ls.append( self.__get_ascii2char( int(s[pTmp: pTmp + 3])) )

            pTmp += 3 

        return "".join(ls)   

#================================================================================   

#         Tool interface    

#================================================================================   

    def is_number(self, value):   

        try:   

            int(value)   

            return True 

        except (TypeError, ValueError):   

            pass 

        return False 

    def is_ascii_range(self, n):   

        return 0 <= n < 256 

    def is_custom_ascii_range(self, n):   

        return 33 <= n <48 or 58 <= n < 126         

class Usage(object):   

    '''''  

     Command line parameter reading and parsing   

    ''' 

    def __init__(self):   

        self._clsWork = Code()   

        self._args_dic = {'arg_help' : ['-?', '-help'],    

                    'arg_p' : ['-p', '-pwd'],   

                    'arg_t' : ['-t', '-text'],   

                    'arg_k' : ['-k', '-key'],   

                    }           

    def help(self, *k):   

        strHelp = "Usage: pwd [-options] [args...] where option include:" 

        strHelp += """  

        -? -help                    print this help message  

        -k <key_str> -p <pwd_str>  

        -k <key_str> -t <text_str>""" 

        print strHelp     

    def args(self, argv_ls):    

        '''''dispatch command'''    

#        print argv_ls   

        if len(argv_ls) <= 1 or len(argv_ls) > 5:   

            print 'Unrecognized option' 

            return 

        cmd_dic = {}   

        curr_cmd = ''  

        # control command   

        for i, v in enumerate(argv_ls[1:]):   

            for j in self._args_dic.items():   

                # add command   

                if v in j[1] and j[0] not in cmd_dic:   

                    curr_cmd = j[0]   

                    cmd_dic[curr_cmd] = []   

                    break 

            else:   

                # add argv   

                if cmd_dic:   

                    cmd_dic[curr_cmd].append(v)               

        # exec command   

        if cmd_dic:   

            self.exec_cmd(cmd_dic)   

        else:   

            print 'Unrecognized option' 

    def exec_cmd(self, cmd_dic):     

        '''''exec cmd'''        

        if len(cmd_dic) == 2:   

            if 'arg_p' in cmd_dic and 'arg_k' in cmd_dic   

                and len(cmd_dic['arg_p']) == 1 and len(cmd_dic['arg_k']) == 1:   

                self._clsWork.reset_key(cmd_dic['arg_k'][0])   

                print self._clsWork.encode(cmd_dic['arg_p'][0])   

                return 

            elif 'arg_t' in cmd_dic and 'arg_k' in cmd_dic   

                and len(cmd_dic['arg_t']) == 1 and len(cmd_dic['arg_k']) == 1:   

                self._clsWork.reset_key(cmd_dic['arg_k'][0])   

                print self._clsWork.decode(cmd_dic['arg_t'][0])   

                return 

        self.help()   

if __name__ == '__main__':   

    usage = Usage()   

    usage.args(sys.argv)

I hope this article has helped you with your Python programming.