Java进行RSA加解密的例子 博客分类: Java java
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2024-03-21 10:30:10
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加密是保证数据安全的手段之一。加密是将纯文本数据转换为难以理解的密文;解密是将密文转换回纯文本。
数据的加解密属于密码学的范畴。通常,加密和解密都需要使用一些秘密信息,这些秘密信息叫做密钥,将纯文本转为密文或者转回的时候都要用到这些密钥。
对称加密指的是发送者和接收者共用同一个密钥的加解密方法。
非对称加密(又称公钥加密)指的是需要一个私有密钥一个公开密钥,两个不同的密钥的加解密体系。尽管不同,这个密钥对的这两个部分在算法上是有关联的。一个密钥将纯文本加密,另一个将密文解密。没有一个密钥能够把加密和加密的功能全部自己完成。公钥,或者用于加密数据的密钥,可以被*分发。
RSA 是基于大整数分解的公钥加密的算法之一。RSA 代表了 Ron Rivest、Adi Shamir 和 Leonard Adleman 三人,RSA 就是他们一起提出的。
以下示例就展示了如何在 Java 中使用 RSA 算法对信息进行加解密。
java.security.KeyPairGenerator 类的实例用于产生一个 RSA 算法的公钥和私钥对,之后将其保存到文件。
javax.crypto.Cipher 类的实例用于使用上面产生的密钥对对信息进行加解密。
import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.PrivateKey; import java.security.PublicKey; import javax.crypto.Cipher; /** * @author JavaDigest * */ public class EncryptionUtil { /** * String to hold name of the encryption algorithm. */ public static final String ALGORITHM = "RSA"; /** * String to hold the name of the private key file. */ public static final String PRIVATE_KEY_FILE = "C:/keys/private.key"; /** * String to hold name of the public key file. */ public static final String PUBLIC_KEY_FILE = "C:/keys/public.key"; /** * Generate key which contains a pair of private and public key using 1024 * bytes. Store the set of keys in Prvate.key and Public.key files. * * @throws NoSuchAlgorithmException * @throws IOException * @throws FileNotFoundException */ public static void generateKey() { try { final KeyPairGenerator keyGen = KeyPairGenerator.getInstance(ALGORITHM); keyGen.initialize(1024); final KeyPair key = keyGen.generateKeyPair(); File privateKeyFile = new File(PRIVATE_KEY_FILE); File publicKeyFile = new File(PUBLIC_KEY_FILE); // Create files to store public and private key if (privateKeyFile.getParentFile() != null) { privateKeyFile.getParentFile().mkdirs(); } privateKeyFile.createNewFile(); if (publicKeyFile.getParentFile() != null) { publicKeyFile.getParentFile().mkdirs(); } publicKeyFile.createNewFile(); // Saving the Public key in a file ObjectOutputStream publicKeyOS = new ObjectOutputStream( new FileOutputStream(publicKeyFile)); publicKeyOS.writeObject(key.getPublic()); publicKeyOS.close(); // Saving the Private key in a file ObjectOutputStream privateKeyOS = new ObjectOutputStream( new FileOutputStream(privateKeyFile)); privateKeyOS.writeObject(key.getPrivate()); privateKeyOS.close(); } catch (Exception e) { e.printStackTrace(); } } /** * The method checks if the pair of public and private key has been generated. * * @return flag indicating if the pair of keys were generated. */ public static boolean areKeysPresent() { File privateKey = new File(PRIVATE_KEY_FILE); File publicKey = new File(PUBLIC_KEY_FILE); if (privateKey.exists() && publicKey.exists()) { return true; } return false; } /** * Encrypt the plain text using public key. * * @param text * : original plain text * @param key * :The public key * @return Encrypted text * @throws java.lang.Exception */ public static byte[] encrypt(String text, PublicKey key) { byte[] cipherText = null; try { // get an RSA cipher object and print the provider final Cipher cipher = Cipher.getInstance(ALGORITHM); // encrypt the plain text using the public key cipher.init(Cipher.ENCRYPT_MODE, key); cipherText = cipher.doFinal(text.getBytes()); } catch (Exception e) { e.printStackTrace(); } return cipherText; } /** * Decrypt text using private key. * * @param text * :encrypted text * @param key * :The private key * @return plain text * @throws java.lang.Exception */ public static String decrypt(byte[] text, PrivateKey key) { byte[] dectyptedText = null; try { // get an RSA cipher object and print the provider final Cipher cipher = Cipher.getInstance(ALGORITHM); // decrypt the text using the private key cipher.init(Cipher.DECRYPT_MODE, key); dectyptedText = cipher.doFinal(text); } catch (Exception ex) { ex.printStackTrace(); } return new String(dectyptedText); } /** * Test the EncryptionUtil */ public static void main(String[] args) { try { // Check if the pair of keys are present else generate those. if (!areKeysPresent()) { // Method generates a pair of keys using the RSA algorithm and stores it // in their respective files generateKey(); } final String originalText = "Text to be encrypted "; ObjectInputStream inputStream = null; // Encrypt the string using the public key inputStream = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE)); final PublicKey publicKey = (PublicKey) inputStream.readObject(); final byte[] cipherText = encrypt(originalText, publicKey); // Decrypt the cipher text using the private key. inputStream = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE)); final PrivateKey privateKey = (PrivateKey) inputStream.readObject(); final String plainText = decrypt(cipherText, privateKey); // Printing the Original, Encrypted and Decrypted Text System.out.println("Original: " + originalText); System.out.println("Encrypted: " +cipherText.toString()); System.out.println("Decrypted: " + plainText); } catch (Exception e) { e.printStackTrace(); } } }
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