java公钥分段加密

转自：https://www.cnblogs.com/runliuv/p/10460793.html

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package javaapplication1;

import java.io.ByteArrayOutputStream;
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.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

/**
 *
 * @author jk
 */
public class RSAUtils {

    /**
     * 加密算法RSA
     */
    public static final String KEY_ALGORITHM = "RSA";

     //  public static final String ECB_PKCS1_PADDING = "RSA";//加密填充方式

      public static final String ECB_PKCS1_PADDING = "RSA/ECB/PKCS1Padding";//加密填充方式

       private static final int _rsa_keysize = 1024;
       
    /**
     * RSA最大加密明文大小,keysize=1024, (1024/8)-11=117
     */
    private static final int MAX_ENCRYPT_BLOCK = (_rsa_keysize/8)-11;

    public static final String _charset = "UTF-8";

    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        String getAgorithm = keyFactory.getAlgorithm();
        getAgorithm = ECB_PKCS1_PADDING;
        Cipher cipher = Cipher.getInstance(getAgorithm);
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /**
     * java端公钥加密
     */
    public static String encryptedDataOnJava(String data, String PUBLICKEY) {
        try {
            data = Base64Utils.encode(encryptByPublicKey(data.getBytes(_charset), PUBLICKEY));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return data;
    }

}