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If you prefer not to use Bouncy Castle for SCrypt and want to rely on the standard Java libraries, you can use the `javax.crypto.SecretKeyFactory` with the `PBKDF2WithHmacSHA256` algorithm for the KDF, and then use `java.security.MessageDigest` for SHA-256 hashing. Here's an example: ```java import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.spec.InvalidKeySpecException; import java.security.spec.KeySpec; import java.util.Arrays; public class KDFWithPBKDF2AndSHA256Example { public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeySpecException { // Replace with your secret key (derived from ECDH or any other source) byte[] secretKeyBytes = hexStringToByteArray("yourSecretKeyInHex"); // Salt for PBKDF2 byte[] salt = generateSalt(); // PBKDF2 parameters int iterationCount = 10000; // You can adjust this based on your security requirements int keyLength = 32; // for a 256-bit key // Use PBKDF2 to derive a key SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256"); KeySpec spec = new PBEKeySpec(byteArrayToCharArray(secretKeyBytes), salt, iterationCount, keyLength * 8); byte[] derivedKey = factory.generateSecret(spec).getEncoded(); // Hash the derived key with SHA-256 byte[] hashedKey = hashWithSHA256(derivedKey); // Print the final key System.out.println("Final Key: " + byteArrayToHexString(hashedKey)); } private static byte[] generateSalt() { // Replace this with a secure method of generating salt // For example, you can use SecureRandom: // SecureRandom random = new SecureRandom(); // byte[] salt = new byte[16]; // random.nextBytes(salt); // return salt; return hexStringToByteArray("yourSaltInHex"); } private static byte[] hashWithSHA256(byte[] input) throws NoSuchAlgorithmException { MessageDigest digest = MessageDigest.getInstance("SHA-256"); return digest.digest(input); } private static byte[] hexStringToByteArray(String hex) { int len = hex.length(); byte[] data = new byte[len / 2]; for (int i = 0; i < len; i += 2) { data[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4) + Character.digit(hex.charAt(i + 1), 16)); } return data; } private static char[] byteArrayToCharArray(byte[] byteArray) { char[] charArray = new char[byteArray.length]; for (int i = 0; i < byteArray.length; i++) { charArray[i] = (char) (byteArray[i] & 0xFF); } return charArray; } private static String byteArrayToHexString(byte[] byteArray) { StringBuilder result = new StringBuilder(); for (byte b : byteArray) { result.append(String.format("%02X", b)); } return result.toString(); } } ``` This example uses the PBKDF2 algorithm with HMAC-SHA-256 for key derivation and SHA-256 for hashing without relying on Bouncy Castle. Remember to replace "yourSecretKeyInHex" and "yourSaltInHex" with the actual secret key and salt in hexadecimal form. Handle exceptions and errors appropriately in a production environment.
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