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If you want to derive separate keys for encryption (enck) and message authentication code (mack) from a master key using a Key Derivation Function (KDF), you can modify the previous example to derive two distinct keys. Here's an example: ```java import javax.crypto.SecretKeyFactory; import javax.crypto.spec.PBEKeySpec; import java.security.NoSuchAlgorithmException; import java.security.spec.InvalidKeySpecException; import java.security.spec.KeySpec; import java.util.Arrays; public class KDFEnckMackExample { public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeySpecException { // Replace with your master key byte[] masterKey = hexStringToByteArray("yourMasterKeyInHex"); // Salt for KDF byte[] salt = generateSalt(); // KDF parameters int iterationCount = 10000; // You can adjust this based on your security requirements int keyLength = 32; // for a 256-bit key // Use KDF to derive encryption key (enck) byte[] enck = deriveKey(masterKey, salt, iterationCount, keyLength); // Use KDF to derive message authentication code key (mack) byte[] mack = deriveKey(masterKey, salt, iterationCount, keyLength); // Print the derived keys System.out.println("Encryption Key (enck): " + byteArrayToHexString(enck)); System.out.println("MAC Key (mack): " + byteArrayToHexString(mack)); } 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[] deriveKey(byte[] masterKey, byte[] salt, int iterationCount, int keyLength) throws NoSuchAlgorithmException, InvalidKeySpecException { SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256"); KeySpec spec = new PBEKeySpec(byteArrayToCharArray(masterKey), salt, iterationCount, keyLength * 8); return factory.generateSecret(spec).getEncoded(); } 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(); } } ``` In this example, the `deriveKey` method is called twice to derive two separate keys (`enck` and `mack`) from the master key. Ensure you replace "yourMasterKeyInHex" and "yourSaltInHex" with your actual master key and a random salt, respectively. Adjust the KDF parameters based on your security requirements.
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