How to use hmac-md5 to encrypt data using Objective C

I am including a code snippet that will show you how to do that.

+(NSData*) calculateHMACMD5WithKey:(NSString*) key andData:(NSString*) data{

const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];

const char *cData = [data cStringUsingEncoding:NSASCIIStringEncoding];

unsigned char cHMAC[CC_MD5_DIGEST_LENGTH];

CCHmac(kCCHmacAlgMD5, cKey, strlen(cKey), cData, strlen(cData), cHMAC);

return [[NSData alloc] initWithBytes:cHMAC length:sizeof(cHMAC)];

}