Signature mechanism

1. Sort all request parameters alphabetically by name. This includes common request parameters and operation-specific parameters, but excludes the Signature parameter.

   For GET requests, these parameters are the part of the request URI that follows the question mark (?) and are separated by ampersands (&).

2. URL-encode the name and value of each sorted request parameter in UTF-8. The encoding rules are as follows:

   Character	Encoding method
   A-Z, a-z, 0-9, and the characters -, _, ., ~	Do not encode.
   Other characters	Encode as %XY, where XY is the hexadecimal representation of the character's ASCII code. For example, a double quotation mark (") is encoded as %22.
   Extended UTF-8 characters	Encode as %XY%ZA….
   A space	Encode as %20 instead of a plus sign (+). This encoding method differs from the standard application/x-www-form-urlencoded Multipurpose Internet Mail Extensions (MIME) format, such as the java.net.URLEncoder implementation in the Java standard library. To produce the correct encoding, first encode the string with a standard library. Then, replace plus signs (+) with %20, asterisks (*) with %2A, and %7E with tildes (~). The following percentEncode method shows this implementation: private static final String ENCODING = "UTF-8"; private static String percentEncode(String value) throws UnsupportedEncodingException { return value != null ? URLEncoder.encode(value, ENCODING).replace("+", "%20").replace("*", "%2A").replace("%7E", "~") : null; }

3. Join the encoded parameter name and value with an equal sign (=).
4. Join the resulting parameter strings with ampersands (&) in the same alphabetical order as in Step 1.a.i. This creates the canonicalized query string.

StringToSign=
      HTTPMethod + “&” +
      percentEncode(“/”) + ”&” +
      percentEncode(CanonicalizedQueryString)

Where:

• HTTPMethod is the HTTP method used for the request, such as GET.
• percentEncode("/") is the forward slash character (/) encoded according to the URL encoding rules in Step 1.a.ii. The encoded value is %2F.
• percentEncode(CanonicalizedQueryString) is the canonicalized query string from Step 1.a, encoded according to the URL encoding rules in Step 1.a.ii.