Java中的非对称加密密码学

密码学是研究和实践不同技术以保护通信免受第三方干扰的学科。它用于网络安全。我们试图开发方法和实践来保护敏感数据。密码学的唯一目标是保护数据免受攻击者的侵害。非对称加密也被称为公钥/私钥加密。私钥如其名，将保持私有，而公钥可以分发。加密是两个密钥之间的数学关联，一个用于加密，另一个用于解密。例如，如果有两个密钥“A1”和“A2”，那么如果密钥“A1”用于加密，“A2”用于解密，反之亦然。

我们使用RSA算法进行非对称加密，首先我们会生成一对密钥（公钥、私钥）。

非对称加密在Java中的密码学

To generate asymmetric key following steps can be followed −

• 首先，我们使用SecureRandom类生成公钥和私钥。它用于生成随机数。

• By using RSA algorithm to generate keys. This class will provide getInstance() method which is used to pass a string variable which signify the key generation algorithm and it returns to key generator object.

• 使用2048位密钥大小初始化密钥生成器对象，并传递随机数。

• Now, the secret key is generated and we want to look at the key we can convert it into hexbinary format by using DatatypeConvertor.

现在实施上述方法 −

Syntax

// Java program to create a
// asymmetric key

package java_cryptography;
import java.security.KeyPair;
import java.security
	.KeyPairGenerator;
import java.security
	.SecureRandom;
import javax.xml.bind
	.DatatypeConverter;

// Class to create an asymmetric key
public class Asymmetric {

	private static final String RSA
		= "RSA";

	// Generating public and private keys
	// using RSA algorithm.
	public static KeyPair generateRSAKkeyPair()
		throws Exception
	{
		SecureRandom secureRandom
			= new SecureRandom();

		KeyPairGenerator keyPairGenerator
			= KeyPairGenerator.getInstance(RSA);

		keyPairGenerator.initialize(
			2048, secureRandom);

		return keyPairGenerator
			.generateKeyPair();
	}

	// Driver code
	public static void main(String args[])
		throws Exception
	{
		KeyPair keypair
			= generateRSAKkeyPair();

		System.out.println(
			"Public Key is: "
			+ DatatypeConverter.printHexBinary(
				keypair.getPublic().getEncoded()));

		System.out.println(
			"Private Key is: "
			+ DatatypeConverter.printHexBinary(
				keypair.getPrivate().getEncoded()));
	}
}

输出

<p style="color:#D2593F;"><img src="/static/imghw/default1.png"  data-src="https://img.php.cn/upload/article/000/465/014/169241191890148.jpg"  class="lazy" alt="Java中的非对称加密密码学" /><b></b></p>

现在可以采取以下步骤来创建程序代码 −

• 我们使用cipher类创建两种不同的模式：加密和解密。加密密钥是私钥，解密密钥是公钥。

• 在密码器上调用doFinal()方法，该方法可以对数据进行单部分操作进行加密/解密，或者完成多部分操作并返回字节数组。

• 最后，我们在使用ENCRYPT_MODE进行加密后得到了密文。

程序，代码

// Java program to perform the
// encryption and decryption
// using asymmetric key

package java_cryptography;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.util.Scanner;

import javax.crypto.Cipher;
import javax.xml.bind
	.DatatypeConverter;

public class Asymmetric {

	private static final String RSA
		= "RSA";
	private static Scanner sc;

	// Generating public & private keys
	// using RSA algorithm.
	public static KeyPair generateRSAKkeyPair()
		throws Exception
	{
		SecureRandom secureRandom = new SecureRandom();
		KeyPairGenerator keyPairGenerator
			= KeyPairGenerator.getInstance(RSA);

		keyPairGenerator.initialize(
			2048, secureRandom);
		return keyPairGenerator
			.generateKeyPair();
	}

	// Encryption function which converts
	// the plainText into a cipherText
	// using private Key.
	public static byte[] do_RSAEncryption(
		String plainText,
		PrivateKey privateKey)
		throws Exception
	{
		Cipher cipher = Cipher.getInstance(RSA);
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		return cipher.doFinal(
			plainText.getBytes());
	}

	// Decryption function which converts
	// the ciphertext back to the
	// original plaintext.
	public static String do_RSADecryption(
		byte[] cipherText,
		PublicKey publicKey)
		throws Exception
	{
		Cipher cipher
			= Cipher.getInstance(RSA);

		cipher.init(Cipher.DECRYPT_MODE,
					publicKey);
		byte[] result
			= cipher.doFinal(cipherText);

		return new String(result);
	}

	// Driver code
	public static void main(String args[])
		throws Exception
	{
		KeyPair keypair
			= generateRSAKkeyPair();

		String plainText = "This is the PlainText "+ "I want to Encrypt using RSA.";

		byte[] cipherText
			= do_RSAEncryption(
				plainText,
				keypair.getPrivate());

		System.out.println(
			"The Public Key is: "
			+ DatatypeConverter.printHexBinary(
				keypair.getPublic().getEncoded()));

		System.out.println(
			"The Private Key is: "
			+ DatatypeConverter.printHexBinary(
				keypair.getPrivate().getEncoded()));

		System.out.print("The Encrypted Text is: ");

		System.out.println(
			DatatypeConverter.printHexBinary(
				cipherText));

		String decryptedText
			= do_RSADecryption(
				cipherText,
				keypair.getPublic());

		System.out.println(
			"The decrypted text is: "
			+ decryptedText);
	}
}

输出

<p style="text-align: center; color: rgb(210, 89, 63);"><img src="/static/imghw/default1.png"  data-src="https://img.php.cn/upload/article/000/465/014/169241191871435.jpg"  class="lazy" alt="Java中的非对称加密密码学" /><b></b></p>

结论

Thus, using RSA algorithm we created encrypted text “This is the PlainText I want to Encrpyt using RSA” in this article.

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