ios - Image download - NSURLSession received Authentication Challenge -

i'm trying download simple image url http://d1vqbpto5tbbz0.cloudfront.net/blog/wp-content/uploads/2014/08/25215844/ios-logo1.png

this simple url access through browser without login.

i have tried code:

nsurlsessionconfiguration *configuration = [nsurlsessionconfiguration defaultsessionconfiguration]; configuration.timeoutintervalforrequest = timeout; nsurlsession *urlsession = [nsurlsession sessionwithconfiguration:configuration delegate:self delegatequeue:nil]; [[urlsession datataskwithurl:urlimage] resume]; 

for receiving authentication challenge.

what reason it?

i have gone through stackoverflow , found these links:

• simple example of nsurlsession authentication

• ios/cocoa - nsurlsession - handling basic https authorization

• nsurlsession basic authentication challenge

in links, there mentioned enter user:password. user name , password, can enter?

you have implement nsurlsessiondelegate protocol method didreceivechallenge.

whenever authentication challenge occurs method calls. , have mention trusted server.

- (void)urlsession:(nsurlsession *)session task:(nsurlsessiontask *)task didreceivechallenge:(nsurlauthenticationchallenge *)challenge  completionhandler:(void (^)(nsurlsessionauthchallengedisposition                              disposition, nsurlcredential *credential))completionhandler {     completionhandler(nsurlsessionauthchallengeusecredential, [nsurlcredential credentialfortrust:challenge.protectionspace.servertrust]); }