Gravatar for Iphone? How do I generate a hexadecimal MD5 hash?

I'd like to use gravatar in my iPhone application. Is there anyway to generate a hexadecimal MD5 hash in Objective-C for iPhone? Using openssl on iPhone is a no-go.

From stackoverflow

• This is how I did it before I removed it from my app:

  #import <CommonCrypto/CommonDigest.h>
  
  NSString* md5( NSString *str ) {
    const char *cStr = [str UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
  
    CC_MD5( cStr, strlen(cStr), result );
  
    return [[NSString
        stringWithFormat:@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
        result[0], result[1],
        result[2], result[3],
        result[4], result[5],
        result[6], result[7],
        result[8], result[9],
        result[10], result[11],
        result[12], result[13],
        result[14], result[15]
        ] lowercaseString];
  }
  

  It's only fair to add that I didn't write this myself. I found it somewhere on the internet but I didn't record where.

• The code I used for generating the necessary MD5 hash is up on my github repository, in the CommonCrypto subfolder. There are a bunch of similar routines in there which will either show you how to use CommonCrypto or how to format strings of hex byte values, base-64, etc.

  A potentially better way of generating the string would be:

  NSMutableString * str = [[NSMutableString alloc] initWithCapacity: 33];
  int i;
  for ( i = 0; i < 16; i++ )
  {
    [str appendFormat: @"%02x", result[i]];
  }
  NSString * output = [str copy];
  [str release];
  return ( [output autorelease] );
  

  If you're going to use the code in the answer above, however, I'd personally suggest changing the %02X's to %02x and forgoing the -lowercaseString call completely-- might as well generate the hex values lowercase to start with.