RSA加密解密

1.自己写一个类RSAUtils把下面的代码添加进去

static class  RSAUtils{        //这里的参数随便写        private static final String PRIVATE_KEY ="1" ;        private static final String PUBLIC_KEY ="2" ;        /**         * 计算出公钥私钥用map存储         * @return         * @throws Exception         */        public static Map<String, Object> genKeyPair() throws Exception {            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");            //这个值关系到块加密的大小，可以更改，但是不要太大，否则效率会低            keyPairGen.initialize(1024);            KeyPair keyPair = keyPairGen.generateKeyPair();            RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();            RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();            Map<String, Object> keyMap = new HashMap<String, Object>(2);            keyMap.put(PUBLIC_KEY, publicKey);            keyMap.put(PRIVATE_KEY, privateKey);            return keyMap;        }        /**         * <p>         * 获取私钥         * </p>         *         * @param keyMap 密钥对         * @return         * @throws Exception         */        public static Key getPrivateKey(Map<String, Object> keyMap)        throws Exception {            Key key = (Key) keyMap.get(PRIVATE_KEY);            return key;            // return Base64Utils.encode(key.getEncoded());        }        /**         * <p>         * 获取公钥         * </p>         *         * @param keyMap 密钥对         * @return         * @throws Exception         */        public static Key getPublicKey(Map<String, Object> keyMap)        throws Exception {            Key key = (Key) keyMap.get(PUBLIC_KEY);            return key;            //return Base64Utils.encode(key.getEncoded());        }        /**         * 加密         *         * @param key  加密的密钥         * @param data 待加密的明文数据         * @return 加密后的数据         * @throws Exception         */        public byte[] encrypt(Key key, byte[] data) throws Exception {            try {                Cipher cipher = Cipher.getInstance("RSA");                cipher.init(Cipher.ENCRYPT_MODE, key);                //获得加密块大小，如:加密前数据为128个byte，而key_size=1024 加密块大小为127 byte,加密后为128个byte;                //因此共有2个加密块，第一个127 byte第二个为1个byte                int blockSize = cipher.getBlockSize();                int outputSize = cipher.getOutputSize(data.length);//获得加密块加密后块大小                int leavedSize = data.length % blockSize;                int blocksSize = leavedSize != 0 ? data.length / blockSize + 1 : data.length / blockSize;                byte[] raw = new byte[outputSize * blocksSize];                int i = 0;                while (data.length - i * blockSize > 0) {                    if (data.length - i * blockSize > blockSize)                        cipher.doFinal(data, i * blockSize, blockSize, raw, i * outputSize);                    else                        cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i * outputSize);                    //这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到ByteArrayOutputStream中                    //，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了OutputSize所以只好用dofinal方法。                    i++;                }                return raw;            } catch (Exception e) {                throw new Exception(e.getMessage());            }        }        /**         * 解密         *         * @param key 解密的密钥         * @param raw 已经加密的数据         * @return 解密后的明文         * @throws Exception         */        public byte[] decrypt(Key key, byte[] raw) throws Exception {            try {                Cipher cipher = Cipher.getInstance("RSA");                cipher.init(cipher.DECRYPT_MODE, key);                int blockSize = cipher.getBlockSize();                ByteArrayOutputStream bout = new ByteArrayOutputStream(64);                int j = 0;                while (raw.length - j * blockSize > 0) {                    bout.write(cipher.doFinal(raw, j * blockSize, blockSize));                    j++;                }                return bout.toByteArray();            } catch (Exception e) {                throw new Exception(e.getMessage());            }        }    }}

2.自己在创建个类Base64Helper把下面的添加进去

import android.util.Base64;public class Base64Helper {//base64编码原文是否是6的整数倍？末尾几个“=”号？public static String encode(byte[] data) {return Base64.encodeToString(data, Base64.DEFAULT);}public static byte[] decode(String str) {return Base64.decode(str, Base64.DEFAULT);}}

3.主布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"    android:layout_width="match_parent" android:layout_height="match_parent"    tools:context="comqq.example.hasee.myapplication.MainActivity"    android:orientation="vertical">    <EditText        android:id="@+id/et"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="Hello World!" />    <Button        android:id="@+id/but1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="加密"        android:onClick="cc"        />    <TextView        android:id="@+id/tv"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <Button        android:id="@+id/but2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="解密"        android:onClick="cc"        />    <TextView        android:id="@+id/tv2"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></LinearLayout>

4.主函数

public class MainActivity extends AppCompatActivity {    private TextView tv,tv2;    private EditText ed;    private Key publicKey,privateKey;    private RSAUtils rsaUtils;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        tv= (TextView) findViewById(R.id.tv);        tv2= (TextView) findViewById(R.id.tv2);        ed= (EditText) findViewById(R.id.et);        try {            //解密用公钥    加密用私钥            Map<String, Object> keyPair = RSAUtils.genKeyPair();            //获取公钥            publicKey = RSAUtils.getPublicKey(keyPair);            //获取私钥            privateKey = RSAUtils.getPrivateKey(keyPair);        } catch (Exception e) {            e.printStackTrace();        }    }    public void cc(View view) throws Exception {                  rsaUtils = new RSAUtils();//实例化工具类        switch (view.getId()) {            case R.id.but1:                //加密                String s = ed.getText().toString();                byte[] bytes = s.getBytes();                try {               //第一个参数是获取得到的私钥    第二个参数是你想要加密的内容                    byte[] encrypt = rsaUtils.encrypt(privateKey, bytes);                    String encode = Base64Helper.encode(encrypt);                    tv.setText(encode);                } catch (Exception e) {                    e.printStackTrace();                }                break;            case R.id.but2:                //解密                String s1 = tv2.getText().toString();                byte[] bytes1 = s1.getBytes();                //第一个参数是获取得到的公钥    第二个参数是你想要解密的暗文                byte[] decrypt = rsaUtils.decrypt(publicKey, bytes1);                tv2.setText(new String(decrypt,0,decrypt.length));                break;        }    }