Implementation of RC4 Encryption and URL encoding in objective c

Question

I've to implement the RC4 encryption algorithm in my application for URL encoding.The sample part is listed below for your reference.

Actual value Before Encryption : 10/28/2013

Expected value After Encryption : ˆ!˜·hÇÔÞò

After URL encoding it should be : %0C%88%21%98%B7h%C7%D4%DE%F2

KEY USED is:@"psw"

I've tried but value after encryption & URL encoding returns in this way:

After encryption : !·hÇÔÞò

After URL encoding : %0C%C2%88%21%C2%98%C2%B7h%C3%87%C3%94%C3%9E%C3%B2

I tried converting the java code into objective c code.The java code works fine ,were as the objective c is not working, which you can see in the above result.

Here is the Java code

import java.net.URLEncoder;

public class RC4 {

private char[] key;
private int[] sbox;
private static final int SBOX_LENGTH = 256;
private static final int KEY_MIN_LENGTH = 1;

public static void main(String[] args) {
    try {
        RC4 rc4 = new RC4("psw");
        char[] result = rc4.encrypt("10/28/2013".toCharArray());
        System.out.println("encrypted string:\n"
                + new String(toByteArray(result)));
        System.out.println("decrypted string:\n"
                + new String(rc4.decrypt(result)));
        System.out.println("decrypted string:\n"
                + URLEncoder.encode(new String(toByteArray(result))));

    } catch (InvalidKeyException e) {
        System.err.println(e.getMessage());
    }

}

static byte[] toByteArray(char[] chars) {
    byte[] bytes = new byte[chars.length];
    for (int i = 0; i < chars.length; i++) {
        // bytes[i*2] = (byte) (chars[i] >> 8);
        bytes[i] = (byte) chars[i];
    }
    return bytes;
}

public RC4(String key) throws InvalidKeyException {
    setKey(key);
}

public RC4() {
}

public char[] decrypt(final char[] msg) {
    return encrypt(msg);
}

public char[] encrypt(final char[] msg) {
    sbox = initSBox(key);
    char[] code = new char[msg.length];
    int i = 0;
    int j = 0;
    for (int n = 0; n < msg.length; n++) {
        i = (i + 1) % SBOX_LENGTH;
        j = (j + sbox[i]) % SBOX_LENGTH;
        swap(i, j, sbox);
        int rand = sbox[(sbox[i] + sbox[j]) % SBOX_LENGTH];
        code[n] = (char) (rand ^ (int) msg[n]);
    }
    return code;
}

private int[] initSBox(char[] key) {
    int[] sbox = new int[SBOX_LENGTH];
    int j = 0;

    for (int i = 0; i < SBOX_LENGTH; i++) {
        sbox[i] = i;
    }

    for (int i = 0; i < SBOX_LENGTH; i++) {
        j = (j + sbox[i] + key[i % key.length]) % SBOX_LENGTH;
        swap(i, j, sbox);
    }
    return sbox;
}

private void swap(int i, int j, int[] sbox) {
    int temp = sbox[i];
    sbox[i] = sbox[j];
    sbox[j] = temp;
}

public void setKey(String key) throws InvalidKeyException {
    if (!(key.length() >= KEY_MIN_LENGTH && key.length() < SBOX_LENGTH)) {
        throw new InvalidKeyException("Key length has to be between "
                + KEY_MIN_LENGTH + " and " + (SBOX_LENGTH - 1));
    }

    this.key = key.toCharArray();
}

public class InvalidKeyException extends Exception {

    private static final long serialVersionUID = 1L;

    public InvalidKeyException(String message) {
        super(message);
    }

}

}

Its corresponding Objective c Code

-(NSString *)encrypt:(NSString *)string{

[self frameSBox:@"psw"];
unichar code[string.length];
const unichar* buffer = code;

int i = 0;
int j = 0;
for (int n = 0; n < string.length; n++) {
    i = (i + 1) % self.SBOX_LENGTH;
    j = (j + [[self.sBox objectAtIndex:i]integerValue]) % self.SBOX_LENGTH;
    [self swap:i with:j];

    int index=([[self.sBox objectAtIndex:i] integerValue]+[[self.sBox objectAtIndex:j] integerValue]);

    int rand=([[self.sBox objectAtIndex:(index%self.SBOX_LENGTH)] integerValue]);

    code[n]=(rand  ^  (int)[string characterAtIndex:n]);
}
buffer = code;
return  [NSString stringWithCharacters:buffer length:string.length];
}


-(NSArray *)frameSBox:(NSString *)keyValue{


   if (self.sBox == nil) {
    self.sBox=[[NSMutableArray alloc]init];
}

self.SBOX_LENGTH=256;    
int j = 0;

for (int i = 0; i < self.SBOX_LENGTH; i++) {
    [self.sBox addObject:[NSNumber numberWithInteger:i]];
}

for (int i = 0; i < self.SBOX_LENGTH; i++) {
    j = (j + [[self.sBox objectAtIndex:i] integerValue] + [keyValue characterAtIndex:(i % keyValue.length)]) % self.SBOX_LENGTH;
    [self swap:i with:j];
}

return self.sBox;
}


-(void)swap:(int)i with:(int)j{

id tempObj = [self.sBox objectAtIndex:i];
[self.sBox replaceObjectAtIndex:i withObject:[self.sBox objectAtIndex:j]];
[self.sBox replaceObjectAtIndex:j withObject:tempObj];

}

   //I'm calling in a different class by creating the RC4encryptor object 
NSString *unescaped =  [[RC4StringEncryptor encryptor] encrypt:@"10/28/2013"];    
logDebug(@"the value is:%@",unescaped);

NSString *escapedString = (NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(
        NULL,
        (__bridge CFStringRef) unescaped,
        NULL,
        CFSTR("!*'();:@&=+$,/?%#[]\" "),
        kCFStringEncodingUTF8));

    NSLog(@"escapedString: %@",escapedString);

I've also tried

#import <CommonCrypto/CommonCryptor.h>
@implementation NSData (RC4)

- (NSData *)RC4EncryptWithKey:(NSString *)key {
char keyPtr[kCCKeySizeMinRC4+1];
bzero(keyPtr, sizeof(keyPtr)); 

[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

NSUInteger dataLength = [self length];

size_t bufferSize = dataLength + kCCKeySizeMinRC4;

void *buffer = malloc(bufferSize);

size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmRC4, kCCModeRC4,
                                      keyPtr, kCCKeySizeMinRC4,
                                      NULL ,
                                      [self bytes], dataLength,
                                      buffer, bufferSize,
                                      &numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
    return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
}

free(buffer);
return nil;
}

- (NSData*) encryptString:(NSString*)plaintext withKey:(NSString*)key {
    return [[plaintext dataUsingEncoding:NSUTF8StringEncoding] RC4EncryptWithKey:key];
}

But this above code doesn't work for me.Kindly help me in this....

Answer 1

Somehow I fixed your code and it encrypts-decrypts perfectly. Here it is:

@interface RC4Crypt()

@property (nonatomic, strong) NSArray * key;
@property (nonatomic, strong) NSMutableArray * sBox;

@end

@implementation RC4Crypt

static const int SBOX_LENGTH = 256;
static const int KEY_MIN_LENGTH = 1;

-(NSString *)encrypt:(NSString *)string withKey:(NSString *)key{

    self.sBox = [[self frameSBox:key] mutableCopy];
    unichar code[string.length];

    int i = 0;
    int j = 0;
    for (int n = 0; n < string.length; n++) {
        i = (i + 1) % SBOX_LENGTH;
        j = (j + [[self.sBox objectAtIndex:i]integerValue]) % SBOX_LENGTH;
        [self.sBox exchangeObjectAtIndex:i withObjectAtIndex:j];

        int index=([self.sBox[i] integerValue]+[self.sBox[j] integerValue]);

        int rand=([self.sBox[(index%SBOX_LENGTH)] integerValue]);

        code[n]=(rand  ^  (int)[string characterAtIndex:n]);
    }
    const unichar* buffer;
    buffer = code;

    return  [NSString stringWithCharacters:buffer length:string.length];
}

- (NSString*) decrypt:(NSString*)string withKey:(NSString*)key
{
    return [self encrypt:string withKey:key];
}


-(NSArray *)frameSBox:(NSString *)keyValue{

    NSMutableArray *sBox = [[NSMutableArray alloc] initWithCapacity:SBOX_LENGTH];

    int j = 0;

    for (int i = 0; i < SBOX_LENGTH; i++) {
    [sBox addObject:[NSNumber numberWithInteger:i]];
    }

    for (int i = 0; i < SBOX_LENGTH; i++) {
        j = (j + [sBox[i] integerValue] + [keyValue characterAtIndex:(i % keyValue.length)]) % SBOX_LENGTH;
        [sBox exchangeObjectAtIndex:i withObjectAtIndex:j];
    }

    return [NSArray arrayWithArray:sBox];
}

@end