urlsigner.m

#import <Foundation/NSString.h>
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonHMAC.h>

// Google Toolbox for Mac is used for Base 64 encoding and decoding
// http://code.google.com/p/google-toolbox-for-mac/
// 1. Download sources with the following command:
//   $svn checkout http://google-toolbox-for-mac.googlecode.com/svn/trunk/ \
//     google-toolbox-for-mac-read-only
// 2. Add the "trunk" directory as a Framework in XCode
// 3. In the XCode "Targets" section, make sure only "urlsigner.m" and
//   "GTMStringEncoding.m" are compiled
#import "GTMStringEncoding.h"

// Sample code demonstrating Maps API URL signing in Objective-C.
int main( int argc, const char *argv[] ) {
  // Sets up the autorelease pool, for memory management.
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

  NSString *key = @"vNIXE0xscrmjlyV-12Nj_BvUPaw=";
  NSString *url =
    @"/maps/api/geocode/json?address=New+York&sensor=false&client=clientID";

  // Stores the url in a NSData.
  NSData *urlData = [url dataUsingEncoding: NSASCIIStringEncoding];

  // URL-safe Base64 coder/decoder.
  GTMStringEncoding *encoding =
    [GTMStringEncoding rfc4648Base64WebsafeStringEncoding];

  // Decodes the URL-safe Base64 key to binary.
  NSData *binaryKey = [encoding decode:key];

  // Signs the URL.
  unsigned char result[CC_SHA1_DIGEST_LENGTH];
  CCHmac(kCCHmacAlgSHA1,
    [binaryKey bytes], [binaryKey length],
    [urlData bytes], [urlData length],
    &result);
  NSData *binarySignature =
    [NSData dataWithBytes:&result length:CC_SHA1_DIGEST_LENGTH];

  // Encodes the signature to URL-safe Base64.
  NSString *signature = [encoding encode:binarySignature];

  NSLog(@"The final URL is: http://maps.googleapis.com/%@&signature=%@", url,
    signature);

  // Clean up autoreleased objects.
  [pool release];
}