blowfish algorithm objective c - iphone

Question

I have to use Blowfish algorithm in my code for encryption and decryption. After calling the decryption method, blowfishDecrypt, I am getting the value in NSData but it give me always null when I convert it to NSString.
I am using the following code :
-(void)methodCalled
{
syncTime=#"c7c937169084b20c3ff882dcda193a59";
NSData* data = [syncTime dataUsingEncoding:NSUTF8StringEncoding];
NSData* data2 = [#"R=U!LH$O2B#" dataUsingEncoding:NSUTF8StringEncoding];
NSData* dycryptData=[self blowfishDecrypt:data usingKey:data2];
// prints <0eec37b6 2b76c2df cdf72356 0f033ed8 d6bd37dd 5223bf66 5c318ebe 07f3cf71>
NSLog(#"%#",dycryptData);
NSString *dSync=[[NSString alloc] initWithBytes:[dycryptData bytes]
length:[dycryptData length]
encoding:NSUTF8StringEncoding];
// prints (null)
NSLog(#"Sync timeis %#",dSync);
}
-(NSData *)blowfishDecrypt:(NSData *)messageData
usingKey:(NSData *)secretKeyData {
NSMutableData *decryptedData = [messageData mutableCopy];
BLOWFISH_CTX ctx;
Blowfish_Init (&ctx, (unsigned char*)[secretKeyData bytes], [secretKeyData length]);
NSRange aLeftRange, aRightRange;
NSData *aLeftBox, *aRightBox;
unsigned long dl = 0, dr = 0;
for (int i = 0; i< [decryptedData length]; i += 8) { // Divide data into octets...
// …and then into quartets
aLeftRange = NSMakeRange(i, 4);
aRightRange = NSMakeRange(i + 4, 4);
aLeftBox = [decryptedData subdataWithRange:aLeftRange];
aRightBox = [decryptedData subdataWithRange:aRightRange];
// Convert bytes into unsigned long
[aLeftBox getBytes:&dl length:sizeof(unsigned long)];
[aRightBox getBytes:&dr length:sizeof(unsigned long)];
// Decipher
Blowfish_Decrypt(&ctx, &dl, &dr);
// Put bytes back
[decryptedData replaceBytesInRange:aLeftRange withBytes:&dl];
[decryptedData replaceBytesInRange:aRightRange withBytes:&dr];
}
return decryptedData;
}
Blowfish library code can be found eg. here

Answer 1

HINT#1 //general answer
NSString provides an initializer for this purpose. You can see more info using the docs here.
NSString * dSync = [[NSString alloc] initWithData: dycryptData
encoding:NSUTF8StringEncoding];
Assuming you use ARC.
HINT#2 // the answer for this particular question
I tried your code and confirm the above NSString conversion returns null. So why it is not working? dycryptData is stream of bytes represented as hex, so I tried the following and received the desired result:
int dycryptData_len = [dycryptData length];
NSMutableString *dSync_hex = [NSMutableString stringWithCapacity:dycryptData_len*2];
const unsigned char *dycryptData_bytes = [dycryptData bytes];
for (int i = 0; i < dycryptData_len; ++i) {
[dSync_hex appendFormat:#"%02x", dycryptData_bytes[i]];
}
NSLog(#"dSync_hex=%#",dSync_hex);
I can see this result in log output:
dSync_hex=0eec37b62b76c2dfcdf723560f033ed8d6bd37dd5223bf665c318ebe07f3cf71