RC4 with Python
import struct,sys,os,binascii
""" RC4加密算法 16*16 S盒 加密单元: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->short def Coding(data): if(len(data)%2): data+=b'\0' dlen = len(data)//2 return(struct.unpack(str(dlen)+'H',data))
# short->bytes def unCoding(data): 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(Keyt) Key=b'' r=0 for i in range(32): k=(Keyt[r%pl]+i)%256 Key+= struct.pack('B',k) r+=1 return Key
#更新密钥 def UpdataKey(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 = tem % 256 return(Coding(Keyo))
if __name__ == '__main__':
#获得输入文件 if len(sys.argv)==1: filename = input('源文件: ') else: filename = sys.argv[1] try: fin = open(filename,'rb') except: print('打开文件失败！') input() sys.exit() print(filename)
#打开输出文件 if filename[-4:]=='.RC4': eID = 1 key=input('输入解密密钥: ').encode() ofilename = filename[:-4] else: eID = 2 key=input('输入加密密钥: ').encode() ofilename = filename+'.RC4'
key = Coding(CreatKey(key)) key = UpdataKey(key) #处理重名 while os.path.exists(ofilename): ofilename = os.path.dirname(ofilename)+ '\\副本 '+ 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(key),dd,len(dd)) key = UpdataKey(key) #crc crc = struct.unpack('I',fin.read(4))[0] if binascii.crc32(x)!=crc: print('CRC32校验错误！',crc,binascii.crc32(x)) input() sys.exit() fout.write(x) #裁剪末尾填充位 fout.truncate(filelen) #加密 elif 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'\0' #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()