DES encrypted value mismatching android and ios - ios

Question

IOS code is
#import "DESCodec.h"
#import <CommonCrypto/CommonCryptor.h>
#implementation DESCodec
{
NSString *key;
}
-(id) init{
self=[super init];
if(self){
key=#"12345678";
}
return self;
}
-(NSString *) decode:(NSString *)encoded{
NSData *inputData = [[NSData alloc] initWithBase64EncodedString:encoded options:0];
NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
size_t outLength;
NSMutableData *outputData = [NSMutableData dataWithLength:(inputData.length +
kCCBlockSizeDES)];
CCCryptorStatus
result = CCCrypt(kCCDecrypt, // operation
kCCAlgorithmDES, // Algorithm
kCCOptionPKCS7Padding , // options
keyData.bytes, // key
keyData.length, // keylength
nil,// iv
inputData.bytes, // dataIn
inputData.length, // dataInLength,
outputData.mutableBytes, // dataOut
outputData.length, // dataOutAvailable
&outLength); // dataOutMoved
if (result != kCCSuccess) {
return nil;
}
[outputData setLength:outLength];
return [[NSString alloc] initWithData:outputData `encoding:NSUTF8StringEncoding];`
}
-(NSString *) encode:(NSString *)decoded{
NSData *inputData = [decoded dataUsingEncoding:NSUTF8StringEncoding];
NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
size_t outLength;
NSMutableData *outputData = [NSMutableData dataWithLength:(inputData.length + kCCBlockSizeDES)];
CCCryptorStatus result = CCCrypt(kCCEncrypt, // operation
kCCAlgorithmDES, // Algorithm
kCCOptionPKCS7Padding, // options
keyData.bytes, // key
keyData.length, // keylength
nil,// iv
inputData.bytes, // dataIn
inputData.length, // dataInLength,
outputData.mutableBytes, // dataOut
outputData.length, // dataOutAvailable
&outLength); // dataOutMoved
if (result != kCCSuccess) {
return nil;
}
[outputData setLength:outLength];
NSString *r = [outputData base64EncodedStringWithOptions:0];
return r;
}
#end
DESCodec *codec=[[DESCodec alloc] init];
NSString *encoded=[codec encode:#"12345678"];
NSString decoded=[codec decode:encoded];
NSLog(#" %# %#",encoded,decoded);
value is ltACiHjVjImOJQ1fTHZkSw== and 12345678
but in java encypted text is "ltACiHjVjIn+uVm31GQvyw=="
I not good in Objective C and I can't able to trigger out the problem.
can anybody please help me. Thanks and regards
Java code is
public class DESCodec {
/**
* Secret key that shall be used for encryption and decryption.
*/
private String strSecretKey = "12345678";
private static final String UNICODE_FORMAT = "UTF-8";
private static final String DES_ENCRYPTION_SCHEME = "DES";
private static final String TAG = "DESCodec";
private Cipher cipher;
private SecretKey key;
public DESCodec() {
try {
this.strSecretKey = strSecretKey;
String myEncryptionScheme = DES_ENCRYPTION_SCHEME;
byte[] keyAsBytes = strSecretKey.getBytes(UNICODE_FORMAT);
DESKeySpec myKeySpec = new DESKeySpec(keyAsBytes);
SecretKeyFactory mySecretKeyFactory = SecretKeyFactory.getInstance(myEncryptionScheme);
cipher = Cipher.getInstance(myEncryptionScheme);
key = mySecretKeyFactory.generateSecret(myKeySpec);
} catch (Exception e) {
e.printStackTrace();
}
}
public String desEncrypt(String message) {
String encryptedString = null;
try {
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] plainText = message.getBytes(UNICODE_FORMAT);
byte[] encryptedText = cipher.doFinal(plainText);
encryptedString = Base64.encodeToString(encryptedText, Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
}
return encryptedString;
}
public String desDecrypt(String message) {
String decryptedText = null;
try {
cipher.init(Cipher.DECRYPT_MODE, key);
byte[] encryptedText = Base64.decode(message, Base64.DEFAULT);
byte[] plainText = cipher.doFinal(encryptedText);
decryptedText = bytes2String(plainText);
} catch (Exception e) {
e.printStackTrace();
}
return decryptedText;
}
private String bytes2String(byte[] bytes) {
try {
return new String(bytes, UNICODE_FORMAT);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return null;
}
}

Answer 1

It's obviously only a problem with the mode of operation, because the first block matches. In Java you're using ECB mode, because "DES" defaults to "DES/ECB/PKCS5Padding". I think that CCCryptor defaults to CBC.
Don't ever use ECB mode. It's not semantically secure. You need to use at least CBC mode with a random IV. The IV doesn't have to be secret, so you can prepend it to the ciphertext. Please look at RNCryptor that has additional security features like authentication of ciphertext. It also has a Java implementation.
Don't use DES anymore. It's not secure anymore. You should use AES. Triple DES is also not that bad.

Answer 2

I hava the same problem when i develop an iOS app.And the android client is used by many people, so i couldn't change the algorithm to AES or others.As Artjom B. said in Java 'DES' defaults to 'DES/ECB/PKCS5Padding', in the source you can find that
Cipher c1 = Cipher.getInstance("DES/ECB/PKCS5Padding");
but unfortunately in iOS you just find that
enum {
kCCOptionPKCS7Padding = 0x0001,
kCCOptionECBMode = 0x0002
}
But finally i find a solution like this
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
kCCAlgorithmDES,
kCCOptionPKCS7Padding | kCCOptionECBMode,
[key UTF8String],
kCCKeySizeDES,
nil,
[cipherData bytes],
[cipherData length],
buffer,
1024,
&numBytesDecrypted);
The importance is kCCOptionPKCS7Padding | kCCOptionECBMode, you can try this method.