getSignatureKey function
Implementation
Future<Uint8List> getSignatureKey(String dateString, String secretAccessKey,
String region, String service) async {
List<int> kDate = Hmac(sha256, utf8.encode('AWS4$secretAccessKey'))
.convert(utf8.encode(dateString))
.bytes;
List<int> kRegion = Hmac(sha256, kDate).convert(utf8.encode(region)).bytes;
List<int> kService =
Hmac(sha256, kRegion).convert(utf8.encode(service)).bytes;
List<int> kSigning =
Hmac(sha256, kService).convert(utf8.encode('aws4_request')).bytes;
return Uint8List.fromList(kSigning);
}