Conversion from decrypted NSData to NSDictionary fails - objective-c

Question

I have to encrypt and scramble a NSDictionary and then unscramble and decrypt in another method. I have followed the instructions from Securely storing keys in iOS Application except that I'm not using a PLIST file to fill the NSDictionary values, but NSString values that are being inputed in the program and I'm doing this targeting OSX
The program can be divided in 3 parts:
Encryption: Encrypts the NSDictionary and returns a base64encoded NSString
Scramble: Scrambles the base64encoded key among the values of the previous NSString
Unscramble and Decryption
My problem is in the last decryption. The unscramble works just fine, but the decryption seems to produce NSData that can't be convertible into the original NSDictionary
Encryption
What I'm doing for encryption is:
Initialising a NSDictionary
Converting it to NSData via NSPropertyListSerialization and format NSPropertyListXMLFormat_v1_0
Encrypting this data using RNCryptor and a key
Returning the base64 representation of this NSData as NSString
The code for this part is:
+(NSString *)encrypt:(NSString *)firstValue secondValue:(NSString *)secondValue andKey:(NSString *)key;
{
NSDictionary *dictionary = [[NSDictionary alloc] initWithObjects:[[NSArray alloc] initWithObjects:firstValue, secondValue, nil] forKeys:[[NSArray alloc] initWithObjects:#"first", #"second", nil]];
NSData *data = [NSPropertyListSerialization dataFromPropertyList:dictionary format:NSPropertyListXMLFormat_v1_0 errorDescription:nil];
NSData *encryptData = [RNEncryptor encryptData:data withSettings:kRNCryptorAES256Settings password:key error:nil];
return [encryptData base64EncodedString];
}
Scramble
The second part of the process is to scramble the key in base64 among the characters of the data, I'm doing this by:
Converting the key to NSData using -(NSData *)dataUsingEncoding:
Converting this NSData to a base64encoded NSString
Inserting char of this NSString into a NSMutadedString in a particular order
Returning NSString from this NSMutadedString to be decrypted later
Here's the code for the scramble part:
+(NSString *)scrambleStrings:(NSString *)firstValue secondValue:(NSString *)secondValue andKey:(NSString *)key;
{
NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
key = [keyData base64EncodedString];
// String from the first method
NSString *encrypt = [self encrypt:firstValue secondValue:secondValue andKey:key];
NSArray *myOrder = [self mySortAlgorithm:key];
NSMutableString *mutableEncrypt = [NSMutableString stringWithString:encrypt];
for(int i=0; i<[myOrder count];i++)
{
unichar c = [key characterAtIndex:i];
int index = [[myOrder objectAtIndex:i] intValue];
[mutableEncrypt insertString:[NSString stringWithCharacters:&c length:1] atIndex:index];
}
return [NSString stringWithString:mutableEncrypt];
}
Decryption
The third part consists of testing if I can decrypt and unscramble it to the original NSDictionary and NSString key. It basically consists of:
Retrieve the scrambled NSString from the second method
Separating the scrambled key from the dictionary NSData from the previous NSString
Decode the base64encode key (Works for sure 'till here)
Decode the base64encoded dictionary data
Decrypt the previous data using RNCryptor using the decoded key
Initialising a NSDictionary using the data from the last step
Output the NSDictionary values via NSLog
And Here's the code for this last part:
+(BOOL)testScrambleWithFirstValue:(NSString *)firstValue secondValue:(NSString *)secondValue andKey:(NSString *)key;
{
NSString *scrambledAndEncryptedKeys = [self scrambleFirstValue:firstValue secondValue:SecondValue andKey:key];
NSArray *myOrder = [self mySortAlgorithm:key];
NSMutableString *encryptedDictionary = [[NSMutableString alloc] init];
NSMutableString *encryptedKey = [[NSMutableString alloc] init];
for (int i=0; i<scrambledAndEncryptedKeys.length; i++) {
char c = [scrambledAndEncryptedKeys characterAtIndex:i];
if ([myOrder doesContain:[NSNumber numberWithInt:i]]) {
[encryptedKey appendFormat:#"%c", c];
} else {
[encryptedDictionary appendFormat:#"%c",c];
}
}
NSString *decryptedKey = [[NSString alloc] initWithData:[NSData dataFromBase64String:[NSString stringWithString:encryptedKey]] encoding:NSUTF8StringEncoding];
NSString *base64DataStr = [[NSString alloc] initWithData:[NSData dataFromBase64String:[NSString stringWithString:encryptedDictionary]] encoding:NSUTF8StringEncoding];
NSData *decryptedData = [RNDecryptor decryptData:[base64DataStr dataUsingEncoding:NSUTF8StringEncoding] withPassword:decryptedKey error:nil];
NSPropertyListFormat xmlFormat;
NSDictionary *decryptedDictionary = [NSPropertyListSerialization propertyListWithData:decryptedData options:NSPropertyListImmutable format:&xmlFormat error:nil];
//Outputs NULL
NSLog(#"decryptedDictionary:%#", decryptedDictionary);
//Just to simplify I'm returning YES here
return YES;
}
The problem is, that the last NSLog outputs a NULL value. Which makes me think that the NSData is not being decrypted.
I've been hammering my head over this since yesterday morning, so all the help is appreciated. Thanks in advance