Apex class for generating an HMAC cookie for tender

gistfile1.js

public class Tender {
    public static String TENDER_SECRET = 'monkey';
    public static String DOMAIN = 'help.yourapp.com';

    public static String tenderize(String username) {
        String expires = '1228117891';
        String input = DOMAIN + '/' + username + '/' + expires;
        Blob hmac = Crypto.generateMac('hmacSHA1', Blob.valueOf(input), Blob.valueOf(TENDER_SECRET));
        return EncodingUtil.convertToHex(hmac);
    }
}