Currently I am getting required data from Magento using REST API, but I have to get these data with out asking login and authorization. How can I do this?
For more details follow the link.
That's what the "Guest" role was created for.
Go in to System > Web Services > REST - Roles > Guest and make sure the endpoint you want to use is enabled for Guest access. Then go to System > Web Services > REST - Attributes > Guest and make sure all the attributes you're trying to access are also enabled. You should now be able to load data from the relevant URL without supplying any credentials.