signature error - string

Question

This shows error "The request signature we calculated does not match the signature you provided. Check your AWS.
string url;
integer statuscode;
String date1=json.serialize(Datetime.now());
if(date1.contains('"')){
date1=date1.replace('"','');}
String algorithmName = 'HmacSHA256';
date1=date1.substring(0,(date1.length()-5));
date1=date1+'Z';
date1=EncodingUtil.UrlEncode(date1,'UTF-8');
String Action=EncodingUtil.UrlEncode('CreateTopic','UTF-8');
String AccessKey=EncodingUtil.UrlEncode('APIKEY','UTF-8'); // API key hide due to security resion but i check it work fine for SES
String Signaturemethod=EncodingUtil.UrlEncode('HmacSHA256','UTF-8');
string str= 'GET\nsns.us-east-1.amazonaws.com\n/\nAction='+Action+'&Name=Testtopics&AWSAccessKeyId='+AccessKey+'&Timestamp='+date1+'&SignatureVersion=2&SignatureMethod='+Signaturemethod;
Blob mac = Crypto.generateMac(algorithmName,Blob.valueOf(str),Blob.valueOf('SECURITYKEY')); //blob value of key used in signature
url='https://sns.us-east-1.amazonaws.com/?Action=CreateTopic&Name=Testtopics&AWSAccessKeyId=ACCESSKEY&Timestamp='+date1+'&SignatureVersion=2&SignatureMethod=HmacSHA256&Signature='+EncodingUtil.UrlEncode(EncodingUtil.base64Encode(mac),'UTF-8'); // final url

Answer 1

I don't have much Idea about the AWS but below is what I was able to find. can't test these things anywhere to figue out the problem.
A common cause of the error message below is not properly creating the string to sign, such as forgetting to URL encode characters such as the colon (:) and the forward slash (/) in Amazon S3 bucket names.
<Error>
<Type>Sender</Type>
<Code>SignatureDoesNotMatch</Code>
<Message>The request signature we calculated does not match the signature you provided.
Check your AWS Secret Access Key and signing method.
Consult the service documentation for details.</Message>
</Error>
http://docs.aws.amazon.com/general/latest/gr/signature-version-2.html
http://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html

Answer 2

It looks like you might be missing a trailing single quote at the end of your url. See if that makes a difference.
url="https://sns.us-east-1.amazonaws.com/?Action=CreateTopic&Name=Testtopics&AWSAccessKeyId=ACCESSKEY&Timestamp='+date1+'&SignatureVersion=2&SignatureMethod=HmacSHA256&Signature='+EncodingUtil.UrlEncode(EncodingUtil.base64Encode(mac),'UTF-8')+"'";