(Java) Generate Encryption Key

Discusses symmetric encryption key generation techniques for block encryption algorithms such as AES, Blowfish, and Twofish, or for other algorithms such as ChaCha20.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // Symmetric encryption algorithms are such that the encryptor and decryptor
    // share a pre-known secret key.  This could be a "single-use" key that is 
    // derived from a secure key exchange algorithm using RSA, ECC, or Diffie-Hellman,
    // or it could be a password known to both sides, or
    // it could simply be the binary bytes of the secret key known in advance on both
    // sides.

    // A secret key has no structure.  It's nothing more than N bytes of data.
    // It should typically be random data, or bytes that resemble random data such
    // as the hash of a password.

    // The number of bytes in the secret key defines the bit-strength of an encryption
    // algorithm.  For example, AES with a 32-byte key is 256-bit AES.  Most algorithms
    // define restrictions on key sizes.  For example, AES has 3 choices: 128-bit, 192-bit,
    // or 256-bit.  In the ChaCha20 algorithm, the key size must always be 256-bits (32-bytes).

    // Both sides (encryptor and decryptor) must be in possession of the same secret key
    // in order to communicate.   Whichever side generates the key, it must somehow
    // deliver the key to the other side beforehand.  Key exchange algorithms, such as RSA, ECC,
    // and Diffie-Hellman define secure ways of exchanging symmetric encryption keys.
    // They do so using asymmetric encryption algorithms (public/private keys).  It is not
    // required to use a key exchange algorithm to achieve the goal of having both sides
    // in possession of the same secret key.  A long-living secret key could be exchanged
    // via any secure out-of-band means.  For example, exchanging the information over a secure
    // TLS (HTTPS) or SSH connection...

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

    boolean success;

    CkCrypt2 crypt = new CkCrypt2();
    crypt.put_CryptAlgorithm("aes");
    crypt.put_KeyLength(256);

    // Generate a 32-byte random secret key,
    // and use it in the crypt object.
    CkPrng prng = new CkPrng();
    String secretKeyHex = prng.genRandom(32,"hex");

    // It is important that the number of bytes in the secret key
    // matches the value specified in the KeyLength property (above).
    crypt.SetEncodedKey(secretKeyHex,"hex");
    System.out.println("randomly generated key: " + secretKeyHex);
  }
}