decrypt value from blowfish in Objective-C code

问题

I am recieving the Encrypted data by server (BLOWFISH ALGORITHM) , I have to decrypt it by using blowfish algorithm in IOS.

you can donwload my code from here : https://www.dropbox.com/s/nswsm7des7isgd5/BlowfishTest-4.zip

I am struggling from 2 days with this task , I try lot of links and find few useful :

Blowfish Source code
How to implement Blowfish algorithm in iOS
http://www.codeding.com/articles/blowfish-encryption-algorithm-for-iphone

In third link, i got ECB ( I have to decrypt using ECB). but this code also not gives correct output after decryption.

I am using a online tool for testing and this shows correct output : http://www.tools4noobs.com/online_tools/decrypt/

Key = 20zE1E47BE57$51
Input value is = aed5c110d793f850521a4dd3a56a70d9
Algorithm = BLOWFISH
Mode = ECB
Decode the input using= Hexa

output = aYzY1380188405  ( this is correct output which i want)

and I am getting : ¹àÀhÒ¢º¹iÂF

Here is my code :

//Mode selected by default in nib: “ECB”
NSString *modeString = [encryptionModeControl titleForSegmentAtIndex:encryptionModeControl.selectedSegmentIndex];
BlowfishAlgorithm *blowFish = [BlowfishAlgorithm new];
[blowFish setMode:[BlowfishAlgorithm buildModeEnum:modeString]];
[blowFish setKey:key];
[blowFish setInitVector:initVector];
[blowFish setupKey];

NSString *cipherText = cipherTextView.text;
NSString *plainText = [blowFish decrypt:cipherText];

NSLog(@"cipher-text: %@", cipherText);
NSLog(@"plain-text: %@", plainText);

Note : Server side data is Encrypted using BLOWFISH in ECB mode, and converted to hexadecimal notation.

回答1:

1) Source of Blowfish routines from David Madore: ftp://quatramaran.ens.fr/pub/madore/misc/blowfish.c

Pls note that in this source .h part should be separated from the .c file.

2) To use Pandora API we have to use the passwords given by its wiki page here: http://pan-do-ra-api.wikia.com/wiki/Json/5/partners

Currently decrypt password is: 20zE1E47BE57$51

3) Use this code snippet (standing on great programmers' shoulders) - original Pandora API implementation is here: https://github.com/alexcrichton/hermes

In AppDelegate.h (for simplicity)

#define PARTNER_DECRYPT  "20zE1E47BE57$51"
...
-(NSData*) PandoraDecrypt:(NSString*) string;

In AppDelegate.m

static char h2i[256] = {
    ['0'] = 0, ['1'] = 1, ['2'] = 2, ['3'] = 3, ['4'] = 4, ['5'] = 5, ['6'] = 6,
    ['7'] = 7, ['8'] = 8, ['9'] = 9, ['a'] = 10, ['b'] = 11, ['c'] = 12,
    ['d'] = 13, ['e'] = 14, ['f'] = 15
};

static void appendByte(unsigned char byte, void *_data) {
    NSMutableData *data = (__bridge NSMutableData*) _data;
    NSLog(@"pre: %@", data);
    [data appendBytes:&byte length:1];
    NSLog(@"post: %@", data);
}

-(NSData*) PandoraDecrypt:(NSString*) string {
    struct blf_ecb_ctx ctx;
    NSMutableData *mut = [[NSMutableData alloc] init];

    Blowfish_ecb_start(&ctx, FALSE, (unsigned char*) PARTNER_DECRYPT,
                       sizeof(PARTNER_DECRYPT) - 1, appendByte,
                       (__bridge void*) mut);

    const char *bytes = [string cStringUsingEncoding:NSASCIIStringEncoding];
    int len = [string lengthOfBytesUsingEncoding:NSASCIIStringEncoding];
    int i;
    for (i = 0; i < len; i += 2) {
        NSLog(@"%c, %c, %d, %d", bytes[i], bytes[i+1], h2i[(int) bytes[i]] * 16, h2i[(int) bytes[i + 1]]);
        Blowfish_ecb_feed(&ctx, h2i[(int) bytes[i]] * 16 + h2i[(int) bytes[i + 1]]);
    }
    Blowfish_ecb_stop(&ctx);

    return mut;
}

And you can use this like:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSLog(@"%@", [NSString stringWithCString:[
                  [self PandoraDecrypt:@"aed5c110d793f850521a4dd3a56a70d9"] bytes]
                           encoding:NSASCIIStringEncoding]);
    return YES;
}

So it was mainly a research from my side, pls give credit to implementers of the Blowfish api and the pandora api ;-) Also my NSLogs are for research purpose, it highlights how the decryption works.

来源：https://stackoverflow.com/questions/19031842/decrypt-value-from-blowfish-in-objective-c-code

标签

ios

objective-c

blowfish