Python implementation method of RC4 file encryption

This paper describes the Python implementation method of RC4 file encryption. Share to everyone for your reference. The specific analysis is as follows:

Based on the RC4 stream encryption algorithm, using the Extended 16*16 s box, the 32-byte key.
It should be more secure at the moment.

Just learning Python, it's hard to adjust.
And in the VC and Python under the implementation of each, two platforms can be decrypted with each other, a sense of accomplishment said.

Here is the implementation in python3.0, which requires a little modification at 2.x.

# for Python 3.0# from Li Bo import struct,sys,os,binascii "" "RC4 encryption algorithm 16*16 s Box encryption unit: Short" "Def RC4 (Pkey,keylen,pin,dlen):     n=65536 S = list (range (n)) j = 0 for I in range (N): j = (j + s[i] + Pkey[i%keylen])%N temp = s[i] s[i] = s[j]    S[J] = Temp i = j = 0 pout= B "for x in Range (Dlen): i = i+1 J = (j + s[i])%N temp = s[i] s[i] = s[j] S[J] = temp pout + = struct.pack (' H ', pin[x]^s[(S[i]+s[j])%N]) return (pout) # Bytes->shortdef Coding (data): if (len (data)%2): data+=b ' Dlen = Len (data)//2 return (Struct.unpack (str (dlen) + ' H ', data)) # Short->bytesdef uncoding (dat A): D=b ' for I in range (len data): D + = Struct.pack (' H ', Data[i]) return (d) #产生32字节密钥def Creatkey (keyt): pl = Len (K EYT) key=b "r=0 for I in range (+): k= (keyt[r%pl]+i)%256 key+= struct.pack (' B ', K) r+=1 return key# update key def up DataKey (KEYT): key = Uncoding (KEYT) #循环左移 key = key[1:] + struct.pack (' B ', key[0]) tem=0 #求和 for I in range (len (Key))  : Tem + = key[i]; KeyO=b ' #Xor for I in range (len (Key)): Keyo + = Struct.pack (' B ', (Key[i]^tem)%256) tem + keyo[i]>>3 tem = TE     M% return (Coding (keyo)) if __name__ = = ' __main__ ': #获得输入文件 If Len (sys.argv) ==1:filename = input (' source file: ') Else: filename = sys.argv[1] Try:fin = open (filename, ' RB ') except:print (' Open file failed! ') input () Sys.exit () print (filename) #打开输出文件 if filename[-4:]== '. RC4 ': EID = 1 key=input (' Input decryption key: '). Encode () Ofilename = filename[:-4] Else:eid = 2 key=input (' Input encryption key: ') . Encode () Ofilename = Filename+ '. RC4 ' key = Coding (Creatkey (key)) key = Updatakey (key) #处理重名 while Os.path.exists (ofilename): Ofilename = Os.path.d    Irname (ofilename) + ' \ \ Copy ' + os.path.basename (ofilename) fout = open (Ofilename, ' WB ') print (ofilename) #解密 if eid==1:      #读文件长度 FileLen = struct.unpack (' I ', Fin.read (4)) [0] Print (' Flielen = ', FileLen, ' \ n ... ') while 1: #读块大小 Ps= Fin.read (2) if not PS: #文件结束 break PAcksize = Struct.unpack (' H ', PS) [0] #读数据 dd=fin.read (packsize) #解密 dd=coding (dd) x = RC4 (Key,len (k EY), Dd,len (dd)) key = Updatakey (key) #crc CRC = Struct.unpack (' I ', Fin.read (4)) [0] if BINASCII.CRC32 (x) !=crc:print (' CRC32 checksum error! ', CRC,BINASCII.CRC32 (x)) input () Sys.exit () fout.write (x) #裁剪末尾填充位 fout.truncate (FileLen) #加密 E    Lif eid==2: #获得文件长度 fin.seek (0,2) FileLen = Fin.tell () print (' Flielen = ', FileLen, ' \ n ... ') Fin.seek (0,0)        Fout.write (Struct.pack (' I ', FileLen)) while 1: #读数据 dd=fin.read (65534) if not DD: #文件结束        Break #末尾填充 srl = len (dd) if srl%2:srl+=1; Dd+=b ' #crc CRC = Struct.pack (' I ', BINASCII.CRC32 (DD)) #加密数据 dd=coding (dd) x = RC4 (Key,len (key) , Dd,len (dd)) key = Updatakey (key) #写入文件 Fout.write (Struct.pack (' H ', srl)) Fout.write (x) fout.write (CRC) Fin.close () Fout.close () print (' Ok! ') Input ()

Hopefully this article will help you with Python programming.

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