Restrict world access to Amazon S3 URLs

I've configured an S3 bucket with CloudFront and using alternate domain name provided by CludFront (I setup the domain alias images.mydomain.com at my DNS zone file). At my DNS host the CNAME I'm pointing to xyz.cloudfront.net. Both my s3 bucket name and CNAME domain alias are images.mydomain.com.

I want world to access my images at http://ift.tt/1zTg6Ow and this is working perfectly.

The problem is the same resource is directly accessible by the world via below two URLs too and I don't want this to happen. I want only http://ift.tt/1zTg6Ow to work for world and not the below two.

http://ift.tt/1zTga0P http://ift.tt/1zTgah3

How do I achieve this? please help.