android RSA加密 解密 非对称可逆加密

android RSA加密 解密 非对称可逆加密

RSA加密 加密使用是生成的公钥 私钥来进行的， 公钥发布出来提供加密功能，私钥负责解密内容。

代码：

/** * Created by liyihang on 17-7-20. sijienet.com */import android.util.Log;import java.math.BigInteger;import java.security.KeyFactory;import java.security.KeyPair;import java.security.KeyPairGenerator;import java.security.NoSuchAlgorithmException;import java.security.interfaces.RSAPrivateKey;import java.security.interfaces.RSAPublicKey;import java.security.spec.RSAPrivateKeySpec;import java.security.spec.RSAPublicKeySpec;import java.util.HashMap;import javax.crypto.Cipher;public class RSAUtils {    public static final String tag = "RSAUtils";    public static void msg(String msg) {        Log.i(tag, msg + "");    }    /**     * 调用测试     */    public static void runs() throws Exception {        msg("开始加密");        HashMap<String, Object> map = RSAUtils.getKeys();        //生成公钥和私钥        RSAPublicKey publicKey = (RSAPublicKey) map.get("public");        RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private");        //模        String modulus = publicKey.getModulus().toString();        //公钥指数        String public_exponent = publicKey.getPublicExponent().toString();        //私钥指数        String private_exponent = privateKey.getPrivateExponent().toString();        //明文        String content = "123456789asd";        //使用模和指数生成公钥和私钥        RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent);        RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent);        //加密后的密文        String mi = RSAUtils.encryptByPublicKey(content, pubKey);        msg(mi);        //解密后的明文        content = RSAUtils.decryptByPrivateKey(mi, priKey);        msg(content);    }    /**     * 生成公钥和私钥     */    public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException {        HashMap<String, Object> map = new HashMap<String, Object>();        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");        keyPairGen.initialize(1024);//密钥长度        KeyPair keyPair = keyPairGen.generateKeyPair();        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();        map.put("public", publicKey);        map.put("private", privateKey);        return map;    }    /**     * 使用模和指数生成RSA公钥     */    public static RSAPublicKey getPublicKey(String modulus, String exponent) {        try {            BigInteger b1 = new BigInteger(modulus);            BigInteger b2 = new BigInteger(exponent);            KeyFactory keyFactory = KeyFactory.getInstance("RSA");            RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);            return (RSAPublicKey) keyFactory.generatePublic(keySpec);        } catch (Exception e) {            e.printStackTrace();            return null;        }    }    /**     * 使用模和指数生成RSA私钥     */    public static RSAPrivateKey getPrivateKey(String modulus, String exponent) {        try {            BigInteger b1 = new BigInteger(modulus);            BigInteger b2 = new BigInteger(exponent);            KeyFactory keyFactory = KeyFactory.getInstance("RSA");            RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);            return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);        } catch (Exception e) {            e.printStackTrace();            return null;        }    }    /**     * 公钥加密     */    public static String encryptByPublicKey(String data, RSAPublicKey publicKey)            throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.ENCRYPT_MODE, publicKey);        // 模长        int key_len = publicKey.getModulus().bitLength() / 8;        // 加密数据长度 <= 模长-11        String[] datas = splitString(data, key_len - 11);        String mi = "";        //如果明文长度大于模长-11则要分组加密        for (String s : datas) {            mi += bcd2Str(cipher.doFinal(s.getBytes()));        }        return mi;    }    /**     * 私钥解密     */    public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey)            throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.DECRYPT_MODE, privateKey);        //模长        int key_len = privateKey.getModulus().bitLength() / 8;        byte[] bytes = data.getBytes();        byte[] bcd = ASCII_To_BCD(bytes, bytes.length);        System.err.println(bcd.length);        //如果密文长度大于模长则要分组解密        String ming = "";        byte[][] arrays = splitArray(bcd, key_len);        for (byte[] arr : arrays) {            ming += new String(cipher.doFinal(arr));        }        return ming;    }    /**     * ASCII码转BCD码     */    public static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {        byte[] bcd = new byte[asc_len / 2];        int j = 0;        for (int i = 0; i < (asc_len + 1) / 2; i++) {            bcd[i] = asc_to_bcd(ascii[j++]);            bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));        }        return bcd;    }    public static byte asc_to_bcd(byte asc) {        byte bcd;        if ((asc >= '0') && (asc <= '9'))            bcd = (byte) (asc - '0');        else if ((asc >= 'A') && (asc <= 'F'))            bcd = (byte) (asc - 'A' + 10);        else if ((asc >= 'a') && (asc <= 'f'))            bcd = (byte) (asc - 'a' + 10);        else            bcd = (byte) (asc - 48);        return bcd;    }    /**     * BCD转字符串     */    public static String bcd2Str(byte[] bytes) {        char temp[] = new char[bytes.length * 2], val;        for (int i = 0; i < bytes.length; i++) {            val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);            temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');            val = (char) (bytes[i] & 0x0f);            temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');        }        return new String(temp);    }    /**     * 拆分字符串     */    public static String[] splitString(String string, int len) {        int x = string.length() / len;        int y = string.length() % len;        int z = 0;        if (y != 0) {            z = 1;        }        String[] strings = new String[x + z];        String str = "";        for (int i = 0; i < x + z; i++) {            if (i == x + z - 1 && y != 0) {                str = string.substring(i * len, i * len + y);            } else {                str = string.substring(i * len, i * len + len);            }            strings[i] = str;        }        return strings;    }    /**     * 拆分数组     */    public static byte[][] splitArray(byte[] data, int len) {        int x = data.length / len;        int y = data.length % len;        int z = 0;        if (y != 0) {            z = 1;        }        byte[][] arrays = new byte[x + z][];        byte[] arr;        for (int i = 0; i < x + z; i++) {            arr = new byte[len];            if (i == x + z - 1 && y != 0) {                System.arraycopy(data, i * len, arr, 0, y);            } else {                System.arraycopy(data, i * len, arr, 0, len);            }            arrays[i] = arr;        }        return arrays;    }}