public class AmazonSqsReceiver
{
    private String getCurrentDate() {
        return DateTime.now().formatGmt('yyyy-MM-dd\'T\'HH:mm:ss.SSS\'Z\'');
    }

    public void receiveMessage() {
        //AmazonAws__c is a custom setting object that stores our keys, an Amazon Host, and a queue name
        //You can just put your keys, host and queue below as strings
        AmazonAws__c aws = AmazonAws__c.getOrgDefaults();

        String accessKey =aws.accessKey__c;
        String secretKey = aws.secretKey__c;
        String host = aws.host__c;
        String queue = aws.queue__c;

        Map<String,String> params = new Map<String,String>();

        params.put('AWSAccessKeyId',encode(accessKey));
        params.put('Action','ReceiveMessage');
        params.put('MaxNumberOfMessages','5');
        params.put('AttributeName','All');
        params.put('SignatureMethod','HmacSHA1');
        params.put('Expires', '2020-04-18T22%3A52%3A43PST');
        params.put('SignatureVersion','2');
        params.put('Version','2009-02-01');

        //The string to sign has to be sorted by keys
        List<String> sortedKeys = new List<String>();
        sortedKeys.addAll(params.keySet());
        sortedKeys.sort();

        String toSign = 'GET\n' + host +'\n'+queue+'\n';
        Integer p = 0;
        for (String key : sortedKeys) {
            String value = params.get(key);
            if (p > 0) {
                toSign += '&';
            }
            p++;
            toSign += key+'='+value;
        }
        params.put('Signature',getMac(toSign,secretKey));

        String url = 'https://'+ host+queue+'?';
        p = 0;
        for (String key : params.keySet()) {
            if (p > 0) {
                url += '&';
            }
            p++;
            url += key+'='+params.get(key);
        }

        HttpRequest req = new HttpRequest();
        req.setEndPoint(url);
        req.setMethod('GET');
        Http http = new Http();
        try {
            //System.debug('Signed string: ' + toSign);
            System.debug('Url: ' + url);
            HttpResponse res = http.send(req);
            System.debug('Status: ' + res.getStatus());
            System.debug('Code  : ' + res.getStatusCode());
            System.debug('Body  : ' + res.getBody());
        }
        catch (System.CalloutException e) {
            System.debug('ERROR: ' + e);
        }

    }
    private String encode(String message){
        return EncodingUtil.urlEncode(message,'UTF-8').replace('+', '%20').replace('*', '%2A').replace('%7E','~');
    }

    private String getMac(String RequestString, String secretkey) {
        String algorithmName = 'hmacSHA1';
        Blob input = Blob.valueOf(RequestString);
        Blob key = Blob.valueOf(secretkey);
        Blob signing =Crypto.generateMac(algorithmName, input, key);
        return EncodingUtil.urlEncode(EncodingUtil.base64Encode(signing), 'UTF-8');
    }

    public static void sendTest() {
        AmazonSqsSender t = new AmazonSqsSender();
        t.sendMessage('Hello from Salesforce ' + Math.random());
    }
}`