zcdziura · July 13, 2023 05:08 · ankushgoyal27 · Mar 10, 2015 · vincentcox · Apr 4, 2016
diff --git a/Crypto Test b/Crypto Test
 import java.io.UnsupportedEncodingException;
 import java.security.InvalidAlgorithmParameterException;
 import java.security.InvalidKeyException;
 import java.security.Key;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.NoSuchAlgorithmException;
 import java.security.NoSuchProviderException;
 import java.security.PrivateKey;
 import java.security.PublicKey;
 import java.security.SecureRandom;
 import java.util.Enumeration;

 import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.KeyAgreement;
 import javax.crypto.NoSuchPaddingException;
 import javax.crypto.SecretKey;
 import javax.crypto.ShortBufferException;
 import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.SecretKeySpec;

 import org.bouncycastle.jce.ECNamedCurveTable;
 import org.bouncycastle.jce.spec.ECNamedCurveParameterSpec;

 public class Test {
    public static byte[] iv = new SecureRandom().generateSeed(16);

    public static void main(String[] args) {
        String plainText = "Look mah, I'm a message!";
        System.out.println("Original plaintext message: " + plainText);

        // Initialize two key pairs
        KeyPair keyPairA = generateECKeys();
        KeyPair keyPairB = generateECKeys();

        // Create two AES secret keys to encrypt/decrypt the message
        SecretKey secretKeyA = generateSharedSecret(keyPairA.getPrivate(),
                keyPairB.getPublic());
        SecretKey secretKeyB = generateSharedSecret(keyPairB.getPrivate(),
                keyPairA.getPublic());

        // Encrypt the message using 'secretKeyA'
        String cipherText = encryptString(secretKeyA, plainText);
        System.out.println("Encrypted cipher text: " + cipherText);

        // Decrypt the message using 'secretKeyB'
        String decryptedPlainText = decryptString(secretKeyB, cipherText);
        System.out.println("Decrypted cipher text: " + decryptedPlainText);
    }

    public static KeyPair generateECKeys() {
        try {
            ECNamedCurveParameterSpec parameterSpec = ECNamedCurveTable.getParameterSpec("brainpoolp256r1");
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(
                    "ECDH", "BC");

            keyPairGenerator.initialize(parameterSpec);
            KeyPair keyPair = keyPairGenerator.generateKeyPair();
           
            return keyPair;
        } catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException
                | NoSuchProviderException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static SecretKey generateSharedSecret(PrivateKey privateKey,
            PublicKey publicKey) {
        try {
            KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH", "BC");
            keyAgreement.init(privateKey);
            keyAgreement.doPhase(publicKey, true);

            SecretKey key = keyAgreement.generateSecret("AES");
            return key;
        } catch (InvalidKeyException | NoSuchAlgorithmException
                | NoSuchProviderException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }

    public static String encryptString(SecretKey key, String plainText) {
        try {
            IvParameterSpec ivSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
            byte[] plainTextBytes = plainText.getBytes("UTF-8");
            byte[] cipherText;

            cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
            cipherText = new byte[cipher.getOutputSize(plainTextBytes.length)];
            int encryptLength = cipher.update(plainTextBytes, 0,
                    plainTextBytes.length, cipherText, 0);
            encryptLength += cipher.doFinal(cipherText, encryptLength);

            return bytesToHex(cipherText);
        } catch (NoSuchAlgorithmException | NoSuchProviderException
                | NoSuchPaddingException | InvalidKeyException
                | InvalidAlgorithmParameterException
                | UnsupportedEncodingException | ShortBufferException
                | IllegalBlockSizeException | BadPaddingException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String decryptString(SecretKey key, String cipherText) {
        try {
            Key decryptionKey = new SecretKeySpec(key.getEncoded(),
                    key.getAlgorithm());
            IvParameterSpec ivSpec = new IvParameterSpec(iv);
            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
            byte[] cipherTextBytes = hexToBytes(cipherText);
            byte[] plainText;

            cipher.init(Cipher.DECRYPT_MODE, decryptionKey, ivSpec);
            plainText = new byte[cipher.getOutputSize(cipherTextBytes.length)];
            int decryptLength = cipher.update(cipherTextBytes, 0,
                    cipherTextBytes.length, plainText, 0);
            decryptLength += cipher.doFinal(plainText, decryptLength);

            return new String(plainText, "UTF-8");
        } catch (NoSuchAlgorithmException | NoSuchProviderException
                | NoSuchPaddingException | InvalidKeyException
                | InvalidAlgorithmParameterException
                | IllegalBlockSizeException | BadPaddingException
                | ShortBufferException | UnsupportedEncodingException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String bytesToHex(byte[] data, int length) {
        String digits = "0123456789ABCDEF";
        StringBuffer buffer = new StringBuffer();

        for (int i = 0; i != length; i++) {
            int v = data[i] & 0xff;

            buffer.append(digits.charAt(v >> 4));
            buffer.append(digits.charAt(v & 0xf));
        }

        return buffer.toString();
    }

    public static String bytesToHex(byte[] data) {
        return bytesToHex(data, data.length);
    }

    public static byte[] hexToBytes(String string) {
        int length = string.length();
        byte[] data = new byte[length / 2];
        for (int i = 0; i < length; i += 2) {
            data[i / 2] = (byte) ((Character.digit(string.charAt(i), 16) << 4) + Character
                    .digit(string.charAt(i + 1), 16));
        }
        return data;
    }
 }
diff --git a/Output b/Output
 Original plaintext message: Look mah, I'm a message!
 Encrypted cipher text: 7AFCF3F9A6213FA6900D3DFC12553379580FC7AD362E2C2E28F548FC2AF42F07CF2B057537376F36
 Decrypted cipher text: Look mah, I'm a message!
	import java.io.UnsupportedEncodingException;
	import java.security.InvalidAlgorithmParameterException;
	import java.security.InvalidKeyException;
	import java.security.Key;
	import java.security.KeyPair;
	import java.security.KeyPairGenerator;
	import java.security.NoSuchAlgorithmException;
	import java.security.NoSuchProviderException;
	import java.security.PrivateKey;
	import java.security.PublicKey;
	import java.security.SecureRandom;
	import java.util.Enumeration;

	import javax.crypto.BadPaddingException;
	import javax.crypto.Cipher;
	import javax.crypto.IllegalBlockSizeException;
	import javax.crypto.KeyAgreement;
	import javax.crypto.NoSuchPaddingException;
	import javax.crypto.SecretKey;
	import javax.crypto.ShortBufferException;
	import javax.crypto.spec.IvParameterSpec;
	import javax.crypto.spec.SecretKeySpec;

	import org.bouncycastle.jce.ECNamedCurveTable;
	import org.bouncycastle.jce.spec.ECNamedCurveParameterSpec;

	public class Test {
	public static byte[] iv = new SecureRandom().generateSeed(16);

	public static void main(String[] args) {
	String plainText = "Look mah, I'm a message!";
	System.out.println("Original plaintext message: " + plainText);

	// Initialize two key pairs
	KeyPair keyPairA = generateECKeys();
	KeyPair keyPairB = generateECKeys();

	// Create two AES secret keys to encrypt/decrypt the message
	SecretKey secretKeyA = generateSharedSecret(keyPairA.getPrivate(),
	keyPairB.getPublic());
	SecretKey secretKeyB = generateSharedSecret(keyPairB.getPrivate(),
	keyPairA.getPublic());

	// Encrypt the message using 'secretKeyA'
	String cipherText = encryptString(secretKeyA, plainText);
	System.out.println("Encrypted cipher text: " + cipherText);

	// Decrypt the message using 'secretKeyB'
	String decryptedPlainText = decryptString(secretKeyB, cipherText);
	System.out.println("Decrypted cipher text: " + decryptedPlainText);
	}

	public static KeyPair generateECKeys() {
	try {
	ECNamedCurveParameterSpec parameterSpec = ECNamedCurveTable.getParameterSpec("brainpoolp256r1");
	KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(
	"ECDH", "BC");

	keyPairGenerator.initialize(parameterSpec);
	KeyPair keyPair = keyPairGenerator.generateKeyPair();

	return keyPair;
	} catch (NoSuchAlgorithmException \| InvalidAlgorithmParameterException
	\| NoSuchProviderException e) {
	e.printStackTrace();
	return null;
	}
	}

	public static SecretKey generateSharedSecret(PrivateKey privateKey,
	PublicKey publicKey) {
	try {
	KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH", "BC");
	keyAgreement.init(privateKey);
	keyAgreement.doPhase(publicKey, true);

	SecretKey key = keyAgreement.generateSecret("AES");
	return key;
	} catch (InvalidKeyException \| NoSuchAlgorithmException
	\| NoSuchProviderException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
	return null;
	}
	}

	public static String encryptString(SecretKey key, String plainText) {
	try {
	IvParameterSpec ivSpec = new IvParameterSpec(iv);
	Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
	byte[] plainTextBytes = plainText.getBytes("UTF-8");
	byte[] cipherText;

	cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
	cipherText = new byte[cipher.getOutputSize(plainTextBytes.length)];
	int encryptLength = cipher.update(plainTextBytes, 0,
	plainTextBytes.length, cipherText, 0);
	encryptLength += cipher.doFinal(cipherText, encryptLength);

	return bytesToHex(cipherText);
	} catch (NoSuchAlgorithmException \| NoSuchProviderException
	\| NoSuchPaddingException \| InvalidKeyException
	\| InvalidAlgorithmParameterException
	\| UnsupportedEncodingException \| ShortBufferException
	\| IllegalBlockSizeException \| BadPaddingException e) {
	e.printStackTrace();
	return null;
	}
	}

	public static String decryptString(SecretKey key, String cipherText) {
	try {
	Key decryptionKey = new SecretKeySpec(key.getEncoded(),
	key.getAlgorithm());
	IvParameterSpec ivSpec = new IvParameterSpec(iv);
	Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
	byte[] cipherTextBytes = hexToBytes(cipherText);
	byte[] plainText;

	cipher.init(Cipher.DECRYPT_MODE, decryptionKey, ivSpec);
	plainText = new byte[cipher.getOutputSize(cipherTextBytes.length)];
	int decryptLength = cipher.update(cipherTextBytes, 0,
	cipherTextBytes.length, plainText, 0);
	decryptLength += cipher.doFinal(plainText, decryptLength);

	return new String(plainText, "UTF-8");
	} catch (NoSuchAlgorithmException \| NoSuchProviderException
	\| NoSuchPaddingException \| InvalidKeyException
	\| InvalidAlgorithmParameterException
	\| IllegalBlockSizeException \| BadPaddingException
	\| ShortBufferException \| UnsupportedEncodingException e) {
	e.printStackTrace();
	return null;
	}
	}

	public static String bytesToHex(byte[] data, int length) {
	String digits = "0123456789ABCDEF";
	StringBuffer buffer = new StringBuffer();

	for (int i = 0; i != length; i++) {
	int v = data[i] & 0xff;

	buffer.append(digits.charAt(v >> 4));
	buffer.append(digits.charAt(v & 0xf));
	}

	return buffer.toString();
	}

	public static String bytesToHex(byte[] data) {
	return bytesToHex(data, data.length);
	}

	public static byte[] hexToBytes(String string) {
	int length = string.length();
	byte[] data = new byte[length / 2];
	for (int i = 0; i < length; i += 2) {
	data[i / 2] = (byte) ((Character.digit(string.charAt(i), 16) << 4) + Character
	.digit(string.charAt(i + 1), 16));
	}
	return data;
	}
	}
	Original plaintext message: Look mah, I'm a message!
	Encrypted cipher text: 7AFCF3F9A6213FA6900D3DFC12553379580FC7AD362E2C2E28F548FC2AF42F07CF2B057537376F36
	Decrypted cipher text: Look mah, I'm a message!