diff --git a/AFNetworking/AFURLConnectionOperation.h b/AFNetworking/AFURLConnectionOperation.h
index 600981c..abd2495 100644
--- a/AFNetworking/AFURLConnectionOperation.h
+++ b/AFNetworking/AFURLConnectionOperation.h
@@ -185,4 +185,10 @@ extern NSString * const AFNetworkingOperationDidFinishNotification;
  */
 - (void)setDownloadProgressBlock:(void (^)(NSInteger bytesRead, NSInteger totalBytesRead, NSInteger totalBytesExpectedToRead))block;
 
+///-------------------------------------------------
+/// @name Setting Authentication Challenge Callbacks
+///-------------------------------------------------
+
+- (void)setAuthenticationChallengeBlock:(void (^)(NSURLConnection *connection, NSURLAuthenticationChallenge *challenge))block;
+
 @end
diff --git a/AFNetworking/AFURLConnectionOperation.m b/AFNetworking/AFURLConnectionOperation.m
index bc8a71e..114cec2 100644
--- a/AFNetworking/AFURLConnectionOperation.m
+++ b/AFNetworking/AFURLConnectionOperation.m
@@ -37,6 +37,7 @@ NSString * const AFNetworkingOperationDidStartNotification = @"com.alamofire.net
 NSString * const AFNetworkingOperationDidFinishNotification = @"com.alamofire.networking.operation.finish";
 
 typedef void (^AFURLConnectionOperationProgressBlock)(NSInteger bytes, NSInteger totalBytes, NSInteger totalBytesExpected);
+typedef void (^AFURLConnectionOperationAuthenticationChallengeBlock)(NSURLConnection *connection, NSURLAuthenticationChallenge *challenge);
 
 static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
     switch (state) {
@@ -64,6 +65,7 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
 @property (readwrite, nonatomic, retain) NSMutableData *dataAccumulator;
 @property (readwrite, nonatomic, copy) AFURLConnectionOperationProgressBlock uploadProgress;
 @property (readwrite, nonatomic, copy) AFURLConnectionOperationProgressBlock downloadProgress;
+@property (readwrite, nonatomic, copy) AFURLConnectionOperationAuthenticationChallengeBlock authenticationBlock;
 
 - (BOOL)shouldTransitionToState:(AFOperationState)state;
 - (void)operationDidStart;
@@ -86,6 +88,7 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
 @synthesize outputStream = _outputStream;
 @synthesize uploadProgress = _uploadProgress;
 @synthesize downloadProgress = _downloadProgress;
+@synthesize authenticationBlock = _authenticationBlock;
 
 + (void)networkRequestThreadEntryPoint:(id)__unused object {
     do {
@@ -136,6 +139,7 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
     	
     [_uploadProgress release];
     [_downloadProgress release];
+    [_authenticationBlock release];
 
     [super dealloc];
 }
@@ -170,6 +174,10 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
     self.downloadProgress = block;
 }
 
+- (void)setAuthenticationChallengeBlock:(void (^)(NSURLConnection *connection, NSURLAuthenticationChallenge *challenge))block {
+    self.authenticationBlock = block;
+}
+
 - (void)setState:(AFOperationState)state {
     if (![self shouldTransitionToState:state]) {
         return;
@@ -305,6 +313,37 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
 
 #pragma mark - NSURLConnectionDelegate
 
+- (void)connection:(NSURLConnection *)connection 
+didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge 
+{
+    if (self.authenticationBlock) {
+        self.authenticationBlock(connection, challenge);
+    } else {
+        if ([challenge previousFailureCount] == 0) {
+            NSURLCredential *credential = nil;
+            
+            NSString *username = [(NSString *)CFURLCopyUserName((CFURLRef)[self.request URL]) autorelease];
+            NSString *password = [(NSString *)CFURLCopyPassword((CFURLRef)[self.request URL]) autorelease];
+            
+            if (username && password) {
+                credential = [NSURLCredential credentialWithUser:username password:password persistence:NSURLCredentialPersistenceNone];
+            } else if (username) {
+                credential = [[[NSURLCredentialStorage sharedCredentialStorage] credentialsForProtectionSpace:[challenge protectionSpace]] objectForKey:username];
+            } else {
+                credential = [[NSURLCredentialStorage sharedCredentialStorage] defaultCredentialForProtectionSpace:[challenge protectionSpace]];
+            }
+            
+            if (credential) {
+                [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];
+            } else {
+                [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];
+            }
+        } else {
+            [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];
+        }
+    }
+}
+
 - (void)connection:(NSURLConnection *)__unused connection 
    didSendBodyData:(NSInteger)bytesWritten 
  totalBytesWritten:(NSInteger)totalBytesWritten