import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.util.Base64;

public class SecretKeyExample {
    public static void main(String[] args) throws Exception {
        // Генерация ключа с помощью KeyGenerator
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(128); // 128-битный ключ
        SecretKey secretKey = keyGen.generateKey();

        // Получение закодированного ключа
        byte[] keyBytes = secretKey.getEncoded();
        System.out.println("Key (Base64): " + Base64.getEncoder().encodeToString(keyBytes));

        // Получение информации о ключе
        System.out.println("Algorithm: " + secretKey.getAlgorithm());
        System.out.println("Format: " + secretKey.getFormat());
    }
}

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import java.security.SecureRandom;
import java.util.Base64;

public class IvParameterSpecExample {
    public static void main(String[] args) throws Exception {
        // Генерация ключа
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(128); // 128-битный ключ
        SecretKey secretKey = keyGen.generateKey();

        // Генерация вектора инициализации
        byte[] iv = new byte[16]; // 16 байт для AES
        SecureRandom random = new SecureRandom();
        random.nextBytes(iv);
        IvParameterSpec ivSpec = new IvParameterSpec(iv);

        // Шифрование с использованием IV
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);

        String originalText = "Hello, Java Crypto!";
        byte[] encryptedBytes = cipher.doFinal(originalText.getBytes());
        System.out.println("Encrypted: " + Base64.getEncoder().encodeToString(encryptedBytes));

        // Дешифрование с использованием IV
        cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
        byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
        System.out.println("Decrypted: " + new String(decryptedBytes));
    }
}

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.util.Base64;

public class KeyPairGeneratorExample {
    public static void main(String[] args) throws Exception {
        // Создание KeyPairGenerator для RSA
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(2048); // 2048-битный ключ

        // Генерация пары ключей
        KeyPair keyPair = keyPairGen.generateKeyPair();

        // Получение открытого и закрытого ключей
        byte[] publicKey = keyPair.getPublic().getEncoded();
        byte[] privateKey = keyPair.getPrivate().getEncoded();

        System.out.println("Public Key (Base64): " + Base64.getEncoder().encodeToString(publicKey));
        System.out.println("Private Key (Base64): " + Base64.getEncoder().encodeToString(privateKey));
    }
}

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;

public class KeyPairExample {
    public static void main(String[] args) throws Exception {
        // Генерация пары ключей
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(2048);
        KeyPair keyPair = keyPairGen.generateKeyPair();

        // Получение открытого и закрытого ключей
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        System.out.println("Public Key Algorithm: " + publicKey.getAlgorithm());
        System.out.println("Private Key Format: " + privateKey.getFormat());
    }
}

public class Task250225 {
    public static void main(String[] args) {
        byte b = (byte) 200;
        int i = b + 100;
        double d = (double) i / 300;

        System.out.println(b);
        System.out.println(i);
        System.out.println(d);
    }
}

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;

public class SignatureExample {
    public static void main(String[] args) throws Exception {
        // Генерация пары ключей
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(2048);
        KeyPair keyPair = keyPairGen.generateKeyPair();

        // Получение ключей
        PrivateKey privateKey = keyPair.getPrivate();
        PublicKey publicKey = keyPair.getPublic();

        // Создание подписи
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privateKey);
        String data = "Hello, Java Crypto!";
        signature.update(data.getBytes());
        byte[] digitalSignature = signature.sign();
        System.out.println("Digital Signature (Base64): " + Base64.getEncoder().encodeToString(digitalSignature));

        // Проверка подписи
        signature.initVerify(publicKey);
        signature.update(data.getBytes());
        boolean isVerified = signature.verify(digitalSignature);
        System.out.println("Signature Verified: " + isVerified);
    }
}

import java.security.MessageDigest;
import java.util.Base64;

public class MessageDigestExample {
    public static void main(String[] args) throws Exception {
        // Создание MessageDigest для SHA-256
        MessageDigest digest = MessageDigest.getInstance("SHA-256");

        // Хэширование данных
        String data = "Hello, Java Crypto!";
        byte[] hash = digest.digest(data.getBytes());

        // Вывод хэша в Base64
        System.out.println("Hash (Base64): " + Base64.getEncoder().encodeToString(hash));
    }
}

M = 77, a = 97, n = 110

M     a     n
01001101 01100001 01101110

010011 010110 000101 101110

010011 → T
010110 → W
000101 → F
101110 → u
Результат кодирования: "TWFu"

"Ma" (2 байта) → TWE=
"M" (1 байт) → TQ==

import java.util.Base64;

public class Base64Example {
    public static void main(String[] args) {
        String originalString = "Hello, Java Crypto API!";
        String encodedString = Base64.getEncoder().encodeToString(originalString.getBytes());
        System.out.println("Encoded: " + encodedString);
    }
}

Encoded: SGVsbG8sIEphdmEgQ3J5cHRvIEFQISTCoA==

import java.util.Base64;

public class Base64DecodeExample {
    public static void main(String[] args) {
        String encodedString = "SGVsbG8sIEphdmEgQ3J5cHRvIEFQISTCoA==";
        byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
        String decodedString = new String(decodedBytes);
        System.out.println("Decoded: " + decodedString);
    }
}

Decoded: Hello, Java Crypto API!

Base64.Encoder encoder = Base64.getEncoder();
Base64.Decoder decoder = Base64.getDecoder();

String encoded = encoder.encodeToString("Test".getBytes());
String decoded = new String(decoder.decode(encoded));

System.out.println("Encoded: " + encoded);
System.out.println("Decoded: " + decoded);

Base64.Encoder urlEncoder = Base64.getUrlEncoder();
Base64.Decoder urlDecoder = Base64.getUrlDecoder();

String encoded = urlEncoder.encodeToString("https://example.com".getBytes());
String decoded = new String(urlDecoder.decode(encoded));

System.out.println("Encoded URL: " + encoded);
System.out.println("Decoded URL: " + decoded);

Base64.Encoder mimeEncoder = Base64.getMimeEncoder();
Base64.Decoder mimeDecoder = Base64.getMimeDecoder();

String encoded = mimeEncoder.encodeToString("Example MIME data".getBytes());
String decoded = new String(mimeDecoder.decode(encoded));

System.out.println("Encoded MIME: " + encoded);
System.out.println("Decoded MIME: " + decoded);

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA..." />

byte[] encryptedData = encryptAES("Hello".getBytes(), secretKey);
String base64Encoded = Base64.getEncoder().encodeToString(encryptedData);

String auth = "user:password";
String encodedAuth = Base64.getEncoder().encodeToString(auth.getBytes());
String header = "Authorization: Basic " + encodedAuth;

public class Task260225 {
    public static void main(String[] args) {
        String value = "10";
        print(value);
        print((byte) value);
        print((Object) value);
    }

    public static void print(String x) {
        System.out.println("String");
    }

    public static void print(byte x) {
        System.out.println("byte");
    }

    public static void print(Object x) {
        System.out.println("Object");
    }
}