使用java实现RSA

时间：2013-04-10 08:31:22

标签： java rsa

我在java中实现RSA我遇到了一个代码，下面给出的代码在解密明文后以数字形式显示明文，但我想用简单的英文输入它。我不想使用java api。

TestRsa.Java 

import java.io.IOException;
import java.math.BigInteger;
import java.util.Random;

public class TestRsa {

    private BigInteger p, q;
    private BigInteger n;
    private BigInteger PhiN;
    private BigInteger e, d;

    public TestRsa() {
        initialize();
    }

    public void initialize() {
        int SIZE = 512;
        /* Step 1: Select two large prime numbers. Say p and q. */
        p = new BigInteger(SIZE, 15, new Random());
        q = new BigInteger(SIZE, 15, new Random());
        /* Step 2: Calculate n = p.q */
        n = p.multiply(q);
        /* Step 3: Calculate ø(n) = (p - 1).(q - 1) */
        PhiN = p.subtract(BigInteger.valueOf(1));
        PhiN = PhiN.multiply(q.subtract(BigInteger.valueOf(1)));
        /* Step 4: Find e such that gcd(e, ø(n)) = 1 ; 1 < e < ø(n) */
        do {
            e = new BigInteger(2 * SIZE, new Random());
        } while ((e.compareTo(PhiN) != 1)
                || (e.gcd(PhiN).compareTo(BigInteger.valueOf(1)) != 0));
        /* Step 5: Calculate d such that e.d = 1 (mod ø(n)) */
        d = e.modInverse(PhiN);
    }

    public BigInteger encrypt(BigInteger plaintext) {
        return plaintext.modPow(e, n);
    }

    public BigInteger decrypt(BigInteger ciphertext) {
        return ciphertext.modPow(d, n);
    }

    public static void main(String[] args) throws IOException {
        TestRsa app = new TestRsa();
        int plaintext;
        System.out.println("Enter any character : ");
        plaintext = System.in.read();
        BigInteger bplaintext, bciphertext;
        bplaintext = BigInteger.valueOf((long) plaintext);
        bciphertext = app.encrypt(bplaintext);
        System.out.println("Plaintext : " + bplaintext.toString());
        System.out.println("Ciphertext : " + bciphertext.toString());
        bplaintext = app.decrypt(bciphertext);
        System.out.println("After Decryption Plaintext : "
                + bplaintext.toString());
    }
}

4 个答案:

答案 0 :(得分：3)

我的RSA课程：

package com.infovale.cripto;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Arrays;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

public class RSA {


static String kPublic = "";
static String kPrivate = "";

public RSA()
{

}


public String Encrypt(String plain) throws NoSuchAlgorithmException,
        NoSuchPaddingException, InvalidKeyException,
        IllegalBlockSizeException, BadPaddingException {

    String encrypted;
    byte[] encryptedBytes;      

    KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
    kpg.initialize(1024);
    KeyPair kp = kpg.genKeyPair();

    PublicKey publicKey = kp.getPublic();
    PrivateKey privateKey = kp.getPrivate();

    byte[] publicKeyBytes = publicKey.getEncoded();
    byte[] privateKeyBytes = privateKey.getEncoded();

    kPublic = bytesToString(publicKeyBytes);
    kPrivate = bytesToString(privateKeyBytes);

    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    encryptedBytes = cipher.doFinal(plain.getBytes());

    encrypted = bytesToString(encryptedBytes);
    return encrypted;

}

public String Decrypt(String result) throws NoSuchAlgorithmException,
        NoSuchPaddingException, InvalidKeyException,
        IllegalBlockSizeException, BadPaddingException {

    byte[] decryptedBytes;

    byte[] byteKeyPrivate = stringToBytes(kPrivate);

    KeyFactory kf = KeyFactory.getInstance("RSA");

    PrivateKey privateKey = null;
    try {

        privateKey = kf.generatePrivate(new PKCS8EncodedKeySpec(byteKeyPrivate));

    } catch (InvalidKeySpecException e) {
        e.printStackTrace();
    }

    String decrypted;

    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, privateKey);
    decryptedBytes = cipher.doFinal(stringToBytes(result));
    decrypted = new String(decryptedBytes);
    return decrypted;

}

public String bytesToString(byte[] b) {
    byte[] b2 = new byte[b.length + 1];
    b2[0] = 1;
    System.arraycopy(b, 0, b2, 1, b.length);
    return new BigInteger(b2).toString(36);
}

public byte[] stringToBytes(String s) {
    byte[] b2 = new BigInteger(s, 36).toByteArray();
    return Arrays.copyOfRange(b2, 1, b2.length);
}
}

答案 1 :(得分：1)

尝试以下几行：

System.out.println("Plaintext : " +  new String(bplaintext.toByteArray() ) );
System.out.println("Ciphertext : " +  new String(bciphertext.toByteArray() ) );
bplaintext = app.decrypt(bciphertext);
        System.out.println("After Decryption Plaintext : " + new String(bplaintext.toByteArray() ) );

答案 2 :(得分：0)

我编辑了Elton Da Costa的类，并添加了该功能以将公钥从String转换为PublicKey类。因为此类用户最终可能希望将公共密钥提供给第三方以对消息进行加密，并将私有密钥随身携带以进行解密。

            package com.custom.util;

            import java.math.BigInteger;
            import java.security.InvalidKeyException;
            import java.security.KeyFactory;
            import java.security.KeyPair;
            import java.security.KeyPairGenerator;
            import java.security.NoSuchAlgorithmException;
            import java.security.PrivateKey;
            import java.security.PublicKey;
            import java.security.spec.InvalidKeySpecException;
            import java.security.spec.PKCS8EncodedKeySpec;
            import java.security.spec.X509EncodedKeySpec;
            import java.util.Arrays;

            import javax.crypto.BadPaddingException;
            import javax.crypto.Cipher;
            import javax.crypto.IllegalBlockSizeException;
            import javax.crypto.NoSuchPaddingException;

            public class RSA {

                static String kPublic = "";
                static String kPrivate = "";

                public RSA() {

                }

                public class KeyPairStrings {
                    private String pubKey;
                    private String privKey;

                    public String getPubKey() {
                        return pubKey;
                    }

                    public String getPrivKey() {
                        return privKey;
                    }

                    @Override
                    public String toString() {
                        return "KeyPairStrings [pubKey=" + pubKey + ", privKey=" + privKey + "]";
                    }



                }

            public KeyPairStrings getKeyPair() throws NoSuchAlgorithmException{

                KeyPairStrings keyPairStrings = new RSA.KeyPairStrings();

                KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
                kpg.initialize(1024);
                KeyPair kp = kpg.genKeyPair();

                PublicKey publicKey = kp.getPublic();
                PrivateKey privateKey = kp.getPrivate();

                byte[] publicKeyBytes = publicKey.getEncoded();
                byte[] privateKeyBytes = privateKey.getEncoded();

                keyPairStrings.pubKey = bytesToString(publicKeyBytes);
                keyPairStrings.privKey = bytesToString(privateKeyBytes);

                return keyPairStrings ;
            }


            public String encrypt(String text , String pubKey) throws NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException, InvalidKeyException{

                byte[] pubKeyByte = stringToBytes(pubKey) ;

                KeyFactory kf = KeyFactory.getInstance("RSA");

                PublicKey publicKey = null;
                try {

                    publicKey = kf.generatePublic(new X509EncodedKeySpec(pubKeyByte));

                } catch (InvalidKeySpecException e) {
                    e.printStackTrace();
                }

                Cipher cipher = Cipher.getInstance("RSA");
                cipher.init(Cipher.ENCRYPT_MODE, publicKey );
                byte[] encryptedBytes = cipher.doFinal(text.getBytes());

                String encrypted = bytesToString(encryptedBytes);

                return encrypted;
            }

            public String decrypt(String encryptedText , String privKey) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{

                byte[] privKeyByte = stringToBytes(privKey) ;

                KeyFactory kf = KeyFactory.getInstance("RSA");

                PrivateKey privateKey = null;
                try {

                    privateKey = kf.generatePrivate(new PKCS8EncodedKeySpec(privKeyByte));

                } catch (InvalidKeySpecException e) {
                    e.printStackTrace();
                }

                String decrypted;

                Cipher cipher = Cipher.getInstance("RSA");
                cipher.init(Cipher.DECRYPT_MODE, privateKey);
                byte[] decryptedBytes = cipher.doFinal(stringToBytes(encryptedText));
                decrypted = new String(decryptedBytes);
                return decrypted;
            }


            public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {

                String text = "hello" ;

                RSA rsa = new RSA();

                KeyPairStrings keyPairStrings =  rsa.getKeyPair() ;

                System.out.println(keyPairStrings);

                String encrypted  = rsa.encrypt(text, keyPairStrings.getPubKey());

                System.out.println("encrypted : "+encrypted);   

                String textResult = rsa.decrypt(encrypted, keyPairStrings.getPrivKey());

                System.out.println("textResult : "+textResult);

            }



                public static String bytesToString(byte[] b) {
                    byte[] b2 = new byte[b.length + 1];
                    b2[0] = 1;
                    System.arraycopy(b, 0, b2, 1, b.length);
                    return new BigInteger(b2).toString(36);
                }

                public byte[] stringToBytes(String s) {
                    byte[] b2 = new BigInteger(s, 36).toByteArray();
                    return Arrays.copyOfRange(b2, 1, b2.length);
                }
            }

答案 3 :(得分：0)

代替这个（仅读取第一个字符）：

int plaintext;
plaintext = System.in.read();
bplaintext = BigInteger.valueOf((long) plaintext);

使用它（读取字符串）：

byte[] plaintext;
plaintext = new Scanner(System.in).nextLine().getBytes();
bplaintext = new BigInteger(plaintext);

然后将其添加到末尾（以将解密的BigInteger转换回字符串）

System.out.println("Original String: " + new String(bplaintext.toByteArray()));
相关问题
最新问题