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
I have a uint_8[] array of characters and I'd like to convert it to an NSString but I'm getting NULL back. What's the proper way to convert between these two types?
// Defined else where as:
uint8_t someValue[8];
someValue is not NULL and contains some valid characters
I've tried:
NSLog(#"converted using CString: %#", [NSString stringWithCString:(char const *)someValue encoding:NSUTF8StringEncoding]);
as well as:
NSMutableData *data = [[NSMutableData alloc] init];
[data appendBytes:someValue length:sizeof(someValue)];
converted = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"converted using NSData: %#", converted);
Using:
[NSString stringWithCString:(char const *)someValue encoding:NSUTF8StringEncoding];
only works if there is a null terminator in the someValue array.
Your other solution doesn't work because sizeof(someValue) does not return the number of characters in the array, it returns the size of the uint8_t pointer.
You can use:
NSUInteger len = ... // the actual number of characters in someValue
NSString *str = [[NSString alloc] initWithBytes:someValue length:len encoding:NSUTF8StringEncoding];
Of course this requires that you know how many characters are really in the array.
I have a NSArray containing NSStrings with emoji codes in the following format:
0x1F463
How can I now convert them into a NSString with the correct format?
With this method I am able to generate an "Emoji"-NSString:
NSString *emoji = [NSString stringWithFormat:#"\U0001F463"];
But this is only possible with constant NSStrings. How can I convert the whole NSArray?
Not my best work, but it appears to work:
for (NSString *string in array)
{
#autoreleasepool {
NSScanner *scanner = [NSScanner scannerWithString:string];
unsigned int val = 0;
(void) [scanner scanHexInt:&val];
NSString *newString = [[NSString alloc] initWithBytes:&val length:sizeof(val) encoding:NSUTF32LittleEndianStringEncoding];
NSLog(#"%#", newString);
[newString release]; // don't use if you're using ARC
}
}
Using an array of four of your sample value, I get four pairs of bare feet.
You can do it like this:
NSString *str = #"0001F463";
// Convert the string representation to an integer
NSScanner *hexScan = [NSScanner scannerWithString:str];
unsigned int hexNum;
[hexScan scanHexInt:&hexNum];
// Make a 32-bit character from the int
UTF32Char inputChar = hexNum;
// Make a string from the character
NSString *res = [[NSString alloc] initWithBytes:&inputChar length:4 encoding:NSUTF32LittleEndianStringEncoding];
// Print the result
NSLog(#"%#", res);
NSString *message = #"testing";
NSUInteger dataLength = [message lengthOfBytesUsingEncoding:NSUnicodeStringEncoding];
void *byteData = malloc( dataLength );
NSRange range = NSMakeRange(0, [message length]);
NSUInteger actualLength = 0;
NSRange remain;
BOOL result = [message getBytes:byteData maxLength:dataLength usedLength:&actualLength encoding:NSUnicodeStringEncoding options:0 range:range remainingRange:&remain];
NSString *decodedString = [[NSString alloc] initWithBytes:byteData length:actualLength encoding:NSUnicodeStringEncoding];
My issue is that I expect decodedString to be testing, but instead it looks like chinese characters. I thought it could be an issue with null-terminated data, but it seems that that should not be an issue.
You want something like this?
NSString *message = #"testing";
NSData *bytes = [message dataUsingEncoding:NSUTF8StringEncoding];
NSString* messageDecoded = [[NSString alloc] initWithData:bytes encoding:NSUTF8StringEncoding];
NSLog(#"decoded: %#", messageDecoded);
The UTF-16 byte order is getting reversed between the encode and decode.
You can do any one of the following:
Use an encoding that specifies an explicit byte order (e.g., NSUTF16BigEndianStringEncoding, NSUTF16LittleEndianStringEncoding, NSUTF8StringEncoding).
Pass NSStringEncodingConversionExternalRepresentation to the options: parameter in getBytes:maxLength:usedLength:encoding:options:range:. This prepends a byte-order mark to the start of the data.
Use NSData, as Elvis suggested.
These days, UTF-8 is the preferred Unicode encoding in most cases.
I'm trying to use the BEncoding ObjC class to decode a .torrent file.
NSData *rawdata = [NSData dataWithContentsOfFile:#"/path/to/the.torrent"];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
When I NSLog torrent I get the following:
{
announce = <68747470 3a2f2f74 6f727265 6e742e75 62756e74 752e636f 6d3a3639 36392f61 6e6e6f75 6e6365>;
comment = <5562756e 74752043 44207265 6c656173 65732e75 62756e74 752e636f 6d>;
"creation date" = 1225365524;
info = {
length = 732766208;
name = <7562756e 74752d38 2e31302d 6465736b 746f702d 69333836 2e69736f>;
"piece length" = 524288;
....
How do I convert the name into a NSString? I have tried..
NSData *info = [torrent valueForKey:#"info"];
NSData *name = [info valueForKey:#"name"];
unsigned char aBuffer[[name length]];
[name getBytes:aBuffer length:[name length]];
NSLog(#"File name: %s", aBuffer);
..which retrives the data, but seems to have additional unicode rubbish after it:
File name: ubuntu-8.10-desktop-i386.iso)
I have also tried (from here)..
NSString *secondtry = [NSString stringWithCharacters:[name bytes] length:[name length] / sizeof(unichar)];
..but this seems to return a bunch of random characters:
扵湵畴㠭ㄮⴰ敤歳潴⵰㍩㘸椮潳
The fact the first way (as mentioned in the Apple documentation) returns most of the data correctly, with some additional bytes makes me think it might be an error in the BEncoding library.. but my lack of knowledge about ObjC is more likely to be at fault..
That's an important point that should be re-emphasized I think. It turns out that,
NSString *content = [NSString stringWithUTF8String:[responseData bytes]];
is not the same as,
NSString *content = [[NSString alloc] initWithBytes:[responseData bytes]
length:[responseData length] encoding: NSUTF8StringEncoding];
the first expects a NULL terminated byte string, the second doesn't. In the above two cases content will be NULL in the first example if the byte string isn't correctly terminated.
How about
NSString *content = [[[NSString alloc] initWithData:myData
encoding:NSUTF8StringEncoding] autorelease];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
When I NSLog torrent I get the following:
{
⋮
}
That would be an NSDictionary, then, not an NSData.
unsigned char aBuffer[[name length]];
[name getBytes:aBuffer length:[name length]];
NSLog(#"File name: %s", aBuffer);
..which retrives the data, but seems to have additional unicode rubbish after it:
File name: ubuntu-8.10-desktop-i386.iso)
No, it retrieved the filename just fine; you simply printed it incorrectly. %s takes a C string, which is null-terminated; the bytes of a data object are not null-terminated (they are just bytes, not necessarily characters in any encoding, and 0—which is null as a character—is a perfectly valid byte). You would have to allocate one more character, and set the last one in the array to 0:
size_t length = [name length] + 1;
unsigned char aBuffer[length];
[name getBytes:aBuffer length:length];
aBuffer[length - 1] = 0;
NSLog(#"File name: %s", aBuffer);
But null-terminating the data in an NSData object is wrong (except when you really do need a C string). I'll get to the right way in a moment.
I have also tried […]..
NSString *secondtry = [NSString stringWithCharacters:[name bytes] length:[name length] / sizeof(unichar)];
..but this seems to return random Chinese characters:
扵湵畴㠭ㄮⴰ敤歳潴⵰㍩㘸椮潳
That's because your bytes are UTF-8, which encodes one character in (usually) one byte.
unichar is, and stringWithCharacters:length: accepts, UTF-16. In that encoding, one character is (usually) two bytes. (Hence the division by sizeof(unichar): it divides the number of bytes by 2 to get the number of characters.)
So you said “here's some UTF-16 data”, and it went and made characters from every two bytes; each pair of bytes was supposed to be two characters, not one, so you got garbage (which turned out to be mostly CJK ideographs).
You answered your own question pretty well, except that stringWithUTF8String: is simpler than stringWithCString:encoding: for UTF-8-encoded strings.
However, when you have the length (as you do when you have an NSData), it is even easier—and more proper—to use initWithBytes:length:encoding:. It's easier because it does not require null-terminated data; it simply uses the length you already have. (Don't forget to release or autorelease it.)
A nice quick and dirty approach is to use NSString's stringWithFormat initializer to help you out. One of the less-often used features of string formatting is the ability to specify a mximum string length when outputting a string. Using this handy feature allows you to convert NSData into a string pretty easily:
NSData *myData = [self getDataFromSomewhere];
NSString *string = [NSString stringWithFormat:#"%.*s", [myData length], [myData bytes]];
If you want to output it to the log, it can be even easier:
NSLog(#"my Data: %.*s", [myData length], [myData bytes]);
Aha, the NSString method stringWithCString works correctly:
With the bencoding.h/.m files added to your project, the complete .m file:
#import <Foundation/Foundation.h>
#import "BEncoding.h"
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// Read raw file, and de-bencode
NSData *rawdata = [NSData dataWithContentsOfFile:#"/path/to/a.torrent"];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
// Get the file name
NSData *infoData = [torrent valueForKey:#"info"];
NSData *nameData = [infoData valueForKey:#"name"];
NSString *filename = [NSString stringWithCString:[nameData bytes] encoding:NSUTF8StringEncoding];
NSLog(#"%#", filename);
[pool drain];
return 0;
}
..and the output:
ubuntu-8.10-desktop-i386.iso
In cases where I don't have control over the data being transformed into a string, such as reading from the network, I prefer to use NSString -initWithBytes:length:encoding: so that I'm not dependent upon having a NULL terminated string in order to get defined results. Note that Apple's documentation says if cString is not a NULL terminated string, that the results are undefined.
Use a category on NSData:
NSData+NSString.h
#interface NSData (NSString)
- (NSString *)toString;
#end
NSData+NSString.m
#import "NSData+NSString.h"
#implementation NSData (NSString)
- (NSString *)toString
{
Byte *dataPointer = (Byte *)[self bytes];
NSMutableString *result = [NSMutableString stringWithCapacity:0];
NSUInteger index;
for (index = 0; index < [self length]; index++)
{
[result appendFormat:#"0x%02x,", dataPointer[index]];
}
return result;
}
#end
Then just NSLog(#"Data is %#", [nsData toString])"
You can try this. Fine with me.
DLog(#"responeData: %#", [[[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSASCIIStringEncoding] autorelease]);
Sometimes you need to create Base64 encoded string from NSData. For instance, when you create a e-mail MIME. In this case use the following:
#import "NSData+Base64.h"
NSString *string = [data base64EncodedString];
This will work.
NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];