// Transformation function for ASP.NET ECW Interop
// qs is the unparsed query string recieved from the calling application with the args1, args2, and args3 key/value pairs
// key is the secret key value, which is converted to a 256bit SHA hash (to ensure a 256 bit encryption key for AES)
private static string Transformation(string qs)
{
if (qs == "")
{
return("error: no query string");
}
string key = ConfigurationManager.AppSettings["ECWCipherKey"].ToString();
if (key == "")
{
return("error: no encryption key");
}
try
{
NameValueCollection qsc = HttpUtility.ParseQueryString(qs);
byte[] cipherText = Convert.FromBase64String(qsc.Get("args1"));
byte[] IV = Convert.FromBase64String(qsc.Get("args2"));
byte[] md5 = Convert.FromBase64String(qsc.Get("args3"));
byte[] test = SIBCrypto.HashMD5(SIBCrypto.Concat(cipherText, IV));
if (md5.SequenceEqual(test) != true)
{
return("error: intregity check failed.");
}
return(ConfigurationManager.AppSettings["ECWInboundRedirectURL"].ToString() + "?" + SIBCrypto.DecryptAES(cipherText, SIBCrypto.HashSHA256(key), IV));
}
catch
{
return("error: transformation failure.");
}
}
// Transformation function for ASP.NET ECW Interop
// qa is the plaintext unparsed query string that is expected to be passed to the receiving application
// key is the secret key value, which is converted to a 256bit SHA hash (to ensure a 256 bit encryption key for AES)
private static string Transformation(string qs)
{
if (qs == "")
{
return("error: no query string");
}
string key = ConfigurationManager.AppSettings["ECWCipherKey"].ToString();
if (key == "")
{
return("error: no encryption key");
}
if (ConfigurationManager.AppSettings["ECWOutboundTimestamp"].ToString().ToLower() == "true")
{
qs = qs + "×tamp=" + SIBTime.UTCTimeStamp();
}
try
{
byte[] IV = SIBCrypto.GenerateAESIV();
byte[] cipherText = SIBCrypto.EncryptAES(qs, SIBCrypto.HashSHA256(key), IV);
byte[] md5 = SIBCrypto.HashMD5(SIBCrypto.Concat(cipherText, IV));
return(ConfigurationManager.AppSettings["ECWOutboundRedirectURL"].ToString() + "?args1=" + SIBCrypto.URLEncode(Convert.ToBase64String(cipherText)) + "&args2=" + SIBCrypto.URLEncode(Convert.ToBase64String(IV)) + "&args3=" + SIBCrypto.URLEncode(Convert.ToBase64String(md5)));
}
catch
{
return("error: transformation failure.");
}
}
