(Tcl) 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 Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

set crypt [new_CkCrypt2]

set 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.)
set saltHex "0102030405060708"

# Generate the 256-bit (32-byte) AES secret key we'll use to decrypt.
set iterationCount 65536
set outputKeyBitLen 256
set secretKeyHex [CkCrypt2_pbkdf2 $crypt $password "utf-8" "sha256" $saltHex $iterationCount $outputKeyBitLen "hex"]

# Setup for 256-bit AES CBC decryption.
CkCrypt2_put_CryptAlgorithm $crypt "aes"
CkCrypt2_put_KeyLength $crypt 256
CkCrypt2_put_CipherMode $crypt "cbc"
CkCrypt2_put_PaddingScheme $crypt 0

# The IV for AES is 16 bytes.
set iv "000102030405060708090A0B0C0D0E0F"
CkCrypt2_SetEncodedIV $crypt $iv "hex"

# Set the secret key for 256-bit AES.
CkCrypt2_SetEncodedKey $crypt $secretKeyHex "hex"

# AES decrypt
# assume our string to decrypt is base64
set strToDecrypt "...."
CkCrypt2_put_EncodingMode $crypt "base64"
set decryptedStr [CkCrypt2_decryptStringENC $crypt $strToDecrypt]

puts "$decryptedStr"

delete_CkCrypt2 $crypt