(Classic ASP) AES 256-bit CBC using PBKDF2 Generated Secret Key

See more Encryption Examples

First generates a 32-byte secret key using PBKDF2 (with HMAC-SHA256), and then uses the secret key to do 256-bit AES CBC mode decryption.

(Duplicates the following Java code)

public String decrypt(String strToDecrypt) {
        try  {
            // Read the initialization vector from the first bytes for the data
            byte [] rawData = Base64.getDecoder().decode(strToDecrypt);
            byte [] iv = new byte[Config.get().encryptionIVLength()];
            byte [] encryptedData = new byte[rawData.length - iv.length];
            System.arraycopy(rawData, 0, iv, 0, iv.length);
            System.arraycopy(rawData, iv.length, encryptedData, 0, encryptedData.length);
 
            IvParameterSpec ivspec = new IvParameterSpec(iv);
 
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
            KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt.getBytes(), 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKeySpec secretKey = new SecretKeySpec(tmp.getEncoded(), "AES");
 
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
            cipher.init(Cipher.DECRYPT_MODE, secretKey, ivspec);
            return new String(cipher.doFinal(encryptedData));
        }
        catch (Exception e) {
            log.error("Could not decrypt the string.", e);
        }
        return null;
    }

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Crypt2")
set crypt = Server.CreateObject("Chilkat.Crypt2")

password = "some arbitrary length password"
' We have 8 bytes of salt encoded using hex.
' (The salt can be any number of bytes, in any desired encoding such as base64, hex, etc.)
saltHex = "0102030405060708"

' Generate the 256-bit (32-byte) AES secret key we'll use to decrypt.
iterationCount = 65536
outputKeyBitLen = 256
secretKeyHex = crypt.Pbkdf2(password,"utf-8","sha256",saltHex,iterationCount,outputKeyBitLen,"hex")

' Setup for 256-bit AES CBC decryption.
crypt.CryptAlgorithm = "aes"
crypt.KeyLength = 256
crypt.CipherMode = "cbc"
crypt.PaddingScheme = 0

' The IV for AES is 16 bytes.
iv = "000102030405060708090A0B0C0D0E0F"
crypt.SetEncodedIV iv,"hex"

' Set the secret key for 256-bit AES.
crypt.SetEncodedKey secretKeyHex,"hex"

' AES decrypt
' assume our string to decrypt is base64
strToDecrypt = "...."
crypt.EncodingMode = "base64"
decryptedStr = crypt.DecryptStringENC(strToDecrypt)

Response.Write "<pre>" & Server.HTMLEncode( decryptedStr) & "</pre>"

%>
</body>
</html>