当您查看 Amazons RESTAuthentication时，您会发现它不使用随机数：

Authorization = "AWS" + " " + AWSAccessKeyId + ":" + Signature;

Signature = Base64( HMAC-SHA1( YourSecretAccessKeyID, UTF-8-Encoding-Of( StringToSign ) ) );

StringToSign = HTTP-Verb + "\n" +
    Content-MD5 + "\n" +
    Content-Type + "\n" +
    Date + "\n" +
    CanonicalizedAmzHeaders +
    CanonicalizedResource;

CanonicalizedResource = [ "/" + Bucket ] +
    <HTTP-Request-URI, from the protocol name up to the query string> +
    [ subresource, if present. For example "?acl", "?location", "?logging", or "?torrent"];

CanonicalizedAmzHeaders = <described below>

这不应该包括一个随机数吗？他们是否以其他方式防范重放攻击？如何？