diff --git a/index.php b/index.php
index a7c2d14..db7e929 100644
--- a/index.php
+++ b/index.php
@@ -775,10 +775,12 @@ HTML;
 
 		//	Get the headers send with the request
 		$headers = getallheaders();
+		//	Ensure the header keys match the format expected by the signature 
+		$headers = array_change_key_case( $headers, CASE_LOWER );
 
 		//	Validate the timestamp is within ±30 seconds
-		if ( !isset( $headers["Date"] ) ) { return null; }	//	No date set
-		$dateHeader = $headers["Date"];
+		if ( !isset( $headers["date"] ) ) { return null; }	//	No date set
+		$dateHeader = $headers["date"];
 		$headerDatetime  = DateTime::createFromFormat('D, d M Y H:i:s T', $dateHeader);
 		$currentDatetime = new DateTime();
 
@@ -802,7 +804,7 @@ HTML;
 
 		//	Validate the Digest
 		//	It is the hash of the raw input string, in binary, encoded as base64
-		$digestString = $headers["Digest"];
+		$digestString = $headers["digest"];
 		//	Usually in the form `SHA-256=Ofv56Jm9rlowLR9zTkfeMGLUG1JYQZj0up3aRPZgT0c=`
 		//	The Base64 encoding may have multiple `=` at the end. So split this at the first `=`
 		$digestData = explode( "=", $digestString, 2 );
@@ -839,7 +841,7 @@ HTML;
 		}
 
 		//	Examine the signature
-		$signatureHeader = $headers["Signature"];
+		$signatureHeader = $headers["signature"];
 
 		// Extract key information from the Signature header
 		$signatureParts = [];
@@ -856,14 +858,13 @@ HTML;
 		foreach ($signatureHeaders as $signatureHeader) {
 			if ( "(request-target)" == $signatureHeader ) {
 				$method = strtolower( $_SERVER["REQUEST_METHOD"] );
-				$target = strtolower( $_SERVER["REQUEST_URI"] );
+				$target =             $_SERVER["REQUEST_URI"];
 				$signatureString .= "(request-target): {$method} {$target}\n";
 			} else if ( "host" == $signatureHeader ) {
 				$host = strtolower( $_SERVER["HTTP_HOST"] );	
 				$signatureString .= "host: {$host}\n";
 			} else {
-				//	In the HTTP header, the keys use Title Case
-				$signatureString .= "{$signatureHeader}: " . $headers[ ucwords( $signatureHeader, "-" ) ] . "\n";
+				$signatureString .= "{$signatureHeader}: " . $headers[$signatureHeader] . "\n";
 			}
 		}