diff --git a/webapp/api.php b/webapp/api.php
index 4ce9936..56ff2ab 100644
--- a/webapp/api.php
+++ b/webapp/api.php
@@ -2483,44 +2483,72 @@ function handlePtrLookup($db) {
 
 /**
  * Make AWS Route53 API request with Signature Version 4
+ * Note: Route53 is a global service, always uses us-east-1 for signing
  */
 function awsRoute53Request($method, $path, $body, $accessKeyId, $secretAccessKey, $region) {
     $service = 'route53';
     $host = 'route53.amazonaws.com';
-    $endpoint = "https://{$host}/{$path}";
+    // Route53 is a global service, always use us-east-1 for signing
+    $signingRegion = 'us-east-1';
 
     $algorithm = 'AWS4-HMAC-SHA256';
     $timestamp = gmdate('Ymd\THis\Z');
     $datestamp = gmdate('Ymd');
 
-    // Create canonical request
-    $canonicalUri = '/' . $path;
+    // Parse path and query string
+    $canonicalUri = '/' . ltrim($path, '/');
     $canonicalQuerystring = '';
 
-    // Parse query string if present
     if (strpos($path, '?') !== false) {
-        list($canonicalUri, $queryString) = explode('?', '/' . $path, 2);
+        list($pathPart, $queryString) = explode('?', $path, 2);
+        $canonicalUri = '/' . ltrim($pathPart, '/');
         parse_str($queryString, $queryParams);
         ksort($queryParams);
-        $canonicalQuerystring = http_build_query($queryParams);
+        // Build query string with proper encoding
+        $pairs = [];
+        foreach ($queryParams as $k => $v) {
+            $pairs[] = rawurlencode($k) . '=' . rawurlencode($v);
+        }
+        $canonicalQuerystring = implode('&', $pairs);
     }
 
-    $payloadHash = hash('sha256', is_array($body) ? json_encode($body) : '');
+    $endpoint = "https://{$host}{$canonicalUri}" . ($canonicalQuerystring ? "?{$canonicalQuerystring}" : '');
 
+    // For GET requests, body is empty
+    $payload = '';
+    if ($method === 'POST' && !empty($body)) {
+        $payload = is_array($body) ? json_encode($body) : $body;
+    }
+    $payloadHash = hash('sha256', $payload);
+
+    // Build canonical headers - must be sorted alphabetically and lowercase
     $canonicalHeaders = "host:{$host}\n" .
                         "x-amz-date:{$timestamp}\n";
     $signedHeaders = 'host;x-amz-date';
 
-    $canonicalRequest = "{$method}\n{$canonicalUri}\n{$canonicalQuerystring}\n{$canonicalHeaders}\n{$signedHeaders}\n{$payloadHash}";
+    // Build canonical request
+    $canonicalRequest = implode("\n", [
+        $method,
+        $canonicalUri,
+        $canonicalQuerystring,
+        $canonicalHeaders,
+        $signedHeaders,
+        $payloadHash
+    ]);
 
     // Create string to sign
-    $credentialScope = "{$datestamp}/{$region}/{$service}/aws4_request";
-    $stringToSign = "{$algorithm}\n{$timestamp}\n{$credentialScope}\n" . hash('sha256', $canonicalRequest);
+    $credentialScope = "{$datestamp}/{$signingRegion}/{$service}/aws4_request";
+    $stringToSign = implode("\n", [
+        $algorithm,
+        $timestamp,
+        $credentialScope,
+        hash('sha256', $canonicalRequest)
+    ]);
 
-    // Calculate signature
+    // Calculate signature using HMAC-SHA256
     $kSecret = 'AWS4' . $secretAccessKey;
     $kDate = hash_hmac('sha256', $datestamp, $kSecret, true);
-    $kRegion = hash_hmac('sha256', $region, $kDate, true);
+    $kRegion = hash_hmac('sha256', $signingRegion, $kDate, true);
     $kService = hash_hmac('sha256', $service, $kRegion, true);
     $kSigning = hash_hmac('sha256', 'aws4_request', $kService, true);
     $signature = hash_hmac('sha256', $stringToSign, $kSigning);
@@ -2537,14 +2565,13 @@ function awsRoute53Request($method, $path, $body, $accessKeyId, $secretAccessKey
         CURLOPT_HTTPHEADER => [
             "Host: {$host}",
             "X-Amz-Date: {$timestamp}",
-            "Authorization: {$authorizationHeader}",
-            "Content-Type: application/xml"
+            "Authorization: {$authorizationHeader}"
         ]
     ]);
 
     if ($method === 'POST') {
         curl_setopt($ch, CURLOPT_POST, true);
-        curl_setopt($ch, CURLOPT_POSTFIELDS, is_array($body) ? json_encode($body) : $body);
+        curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
     }
 
     $response = curl_exec($ch);