I have a PHP script that creates a QR code out of a username and timestamp. I need to prove the QR code came from my server so I am encrypting the username and timestamp with a private RSA key. In order to get it into the QR code I am then base64 encoding it.
I am trialling it with Android first. I can get the string out of the QR code but when I base64 decode it in Android, it returns null. After debugging it seems it's because there are two whitespaces in the string. When the decoder comes to check the illegal characters are divisible by 4, it obviously fails. Getting desperate I removed the whitespaces but then it changed the length so the calculations still didn't work out. Can I change the whitespace for a 'safe' character? Or is the particular encode/decode pair not compatible??
PHP code:
$data = base64_encode($username."`".$timestamp); $fp = fopen("private.pem", "r"); $private_key = fread($fp, 8192); fclose($fp); openssl_private_encrypt($data, &$encrypted_data, $private_key); $encrypted_data_64 = base64_encode($encrypted_data); // create QR code Android code:
String s = data.getStringExtra("SCAN_RESULT"); byte[] b = Base64.decode(s.toCharArray()); // b is null at this point Base64 code that it bugs out on:is
// Check special case int sLen = str != null ? str.length() : 0; if (sLen == 0) return new byte[0]; // Count illegal characters (including '\r', '\n') to know what size the returned array will be, // so we don't have to reallocate & copy it later. int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...) for (int i = 0; i < sLen; i++) // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out. if (IA[str.charAt(i)] < 0) sepCnt++; // Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045. if ((sLen - sepCnt) % 4 != 0) return null; 
$encrypted_data_64is not an empty string? Don't know how to fix Andriod though :)