首先我們可以從看到:明文--->公開金鑰--->密文 密文-->密鑰-->明文
RSA由於public key<公開金鑰> 和private key<密鑰>的不同<也叫非對稱演算法加解密>,極大的提高了檔案的安全性。 對稱演算法是同key的 ,這樣很容易被人破解。
RSA演算法:
- import java.security.Key;
- import java.security.KeyFactory;
- import java.security.KeyPair;
- import java.security.KeyPairGenerator;
- import java.security.PrivateKey;
- import java.security.PublicKey;
- import java.security.interfaces.RSAPrivateKey;
- import java.security.interfaces.RSAPublicKey;
- import java.security.spec.PKCS8EncodedKeySpec;
- import java.security.spec.X509EncodedKeySpec;
-
- import javax.crypto.Cipher;
-
- import sun.misc.BASE64Decoder;
- import sun.misc.BASE64Encoder;
-
-
- public class RSAHelper {
-
-
- public static PublicKey getPublicKey(String key) throws Exception {
- byte[] keyBytes;
- keyBytes = (new BASE64Decoder()).decodeBuffer(key);
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- X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
- KeyFactory keyFactory = KeyFactory.getInstance("RSA");
- PublicKey publicKey = keyFactory.generatePublic(keySpec);
- return publicKey;
- }
-
- public static PrivateKey getPrivateKey(String key) throws Exception {
- byte[] keyBytes;
- keyBytes = (new BASE64Decoder()).decodeBuffer(key);
-
- PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
- KeyFactory keyFactory = KeyFactory.getInstance("RSA");
- PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
- return privateKey;
- }
-
-
- public static String getKeyString(Key key) throws Exception {
- byte[] keyBytes = key.getEncoded();
- String s = (new BASE64Encoder()).encode(keyBytes);
- return s;
- }
-
-
- public static void main(String[] args) throws Exception {
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- KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
- //密鑰位元
- keyPairGen.initialize(1024);
- //金鑰組
- KeyPair keyPair = keyPairGen.generateKeyPair();
-
- // 公開金鑰
- PublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
-
- // 私密金鑰
- PrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
-
- String publicKeyString = getKeyString(publicKey);
- System.out.println("public:/n" + publicKeyString);
-
- String privateKeyString = getKeyString(privateKey);
- System.out.println("private:/n" + privateKeyString);
-
- //加解密類
- Cipher cipher = Cipher.getInstance("RSA");//Cipher.getInstance("RSA/ECB/PKCS1Padding");
-
- //明文
- byte[] plainText = "我們都很好!郵件:@sina.com".getBytes();
-
- //加密
- cipher.init(Cipher.ENCRYPT_MODE, publicKey);
- byte[] enBytes = cipher.doFinal(plainText);
-
- //通過密鑰字串得到密鑰
- publicKey = getPublicKey(publicKeyString);
- privateKey = getPrivateKey(privateKeyString);
-
- //解密
- cipher.init(Cipher.DECRYPT_MODE, privateKey);
- byte[]deBytes = cipher.doFinal(enBytes);
-
- publicKeyString = getKeyString(publicKey);
- System.out.println("public:/n" +publicKeyString);
-
- privateKeyString = getKeyString(privateKey);
- System.out.println("private:/n" + privateKeyString);
-
- String s = new String(deBytes);
- System.out.println(s);
-
-
- }
-
- }
在實際開發中! 我們通過自己的modulus ,publicExponent 這兩個是使用者加密產生public key 而 privateExponet 用於產生private key 來開發的情況比較多。
- import java.math.BigInteger;
-
- import java.security.KeyFactory;
-
- import java.security.PrivateKey;
-
- import java.security.PublicKey;
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- import java.security.spec.RSAPrivateKeySpec;
-
- import java.security.spec.RSAPublicKeySpec;
-
-
-
- import javax.crypto.Cipher;
-
-
-
- public class RsaKey {
-
-
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- public PublicKey getPublicKey(String modulus,String publicExponent) throws Exception {
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- BigInteger m = new BigInteger(modulus);
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- BigInteger e = new BigInteger(publicExponent);
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- RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m,e);
-
- KeyFactory keyFactory = KeyFactory.getInstance("RSA");
- PublicKey publicKey = keyFactory.generatePublic(keySpec);
-
- return publicKey;
-
- }
-
-
-
- public PrivateKey getPrivateKey(String modulus,String privateExponent) throws Exception {
-
- BigInteger m = new BigInteger(modulus);
-
- BigInteger e = new BigInteger(privateExponent);
-
- RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m,e);
-
- KeyFactory keyFactory = KeyFactory.getInstance("RSA");
-
- PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
-
- return privateKey;
-
- }
-
-
-
- public static void main(String[] args) throws Exception {
-
- String modulus = "10103166745709600780215616551837697832816413714471062522342538060943596036859967333870827790358555455232243383580565187280643159050869924436081447583051139";
-
- String publicExponent = "65537";
-
- String privateExponet = "367979294475011322800474185715497882523349856362702385535371444397399388741997039894583483410120364529325888461124714276674612930833020362278754665756193";
-
-
-
- RsaKey key = new RsaKey();
-
- PublicKey publicKey = key.getPublicKey(modulus, publicExponent);
-
- PrivateKey privateKey = key.getPrivateKey(modulus, privateExponet);
-
-
-
-
-
- //加解密類
-
- Cipher cipher = Cipher.getInstance("RSA"); //"RSA/ECB/PKCS1Padding" 就是:“演算法/工作模式/填充模式”
-
-
-
- //明文
-
- byte[] plainText = "hello world !".getBytes();
-
-
-
- //加密
-
- cipher.init(Cipher.ENCRYPT_MODE, publicKey);
-
- byte[] enBytes = cipher.doFinal(plainText);
-
-
-
-
-
- cipher.init(Cipher.DECRYPT_MODE, privateKey);
-
- byte[]deBytes = cipher.doFinal(enBytes);
-
-
-
- String s = new String(deBytes);
-
- System.out.println(s);
-
-
-
- }
- }