iOS MD5加密方法

- (NSString*) md5HexDigest(NSString *string) 

{ 

 const char *original_str = [string UTF8String]; 

 unsigned char result[CC_MD5_DIGEST_LENGTH]; 

 CC_MD5(original_str, strlen(original_str), result); 

 NSMutableString *hash = [NSMutableString string]; 

 for (int i = 0; i < 16; i++) 

 [hash appendFormat:@"%02X", result[i]]; 

 return [hash lowercaseString]; 

}