Android 获取签名公钥和公钥私钥加解密的方法(推荐)

如下所示：

public class getpublickey {
   
  /**
   * 获取签名公钥
   * @param mcontext
   * @return
   */
  protected static string getsigninfo(context mcontext) {
    string signcode = "";
    try {
      packageinfo packageinfo = mcontext.getpackagemanager().getpackageinfo(
          getappinfo.getpackagename(mcontext), packagemanager.get_signatures);
      signature[] signs = packageinfo.signatures;
      signature sign = signs[0];
 
      signcode = parsesignature(sign.tobytearray());
      signcode = signcode.tolowercase();
    } catch (exception e) {
      log.e(constants.tag, e.getmessage(), e);
    }
    return signcode;
  }
 
  protected static string parsesignature(byte[] signature) {
    string sign = "";
    try {
      certificatefactory certfactory = certificatefactory
          .getinstance("x.509");
      x509certificate cert = (x509certificate) certfactory
          .generatecertificate(new bytearrayinputstream(signature));
      string pubkey = cert.getpublickey().tostring();
      string ss = substring(pubkey);
      ss = ss.replace(",", "");
      ss = ss.tolowercase();
      int aa = ss.indexof("modulus");
      int bb = ss.indexof("publicexponent");
      sign = ss.substring(aa + 8, bb);
    } catch (certificateexception e) {
      log.e(constants.tag, e.getmessage(), e);
    }
    return sign;
  }
 
  public static string substring(string sub) {
    pattern pp = pattern.compile("\\s*|\t|\r|\n");
    matcher mm = pp.matcher(sub);
    return mm.replaceall("");
  }
}



package com.example.xscamera;
 
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;
 
/**
 * <p>
 * rsa公钥/私钥/签名工具包
 * <p>
 * 字符串格式的密钥在未在特殊说明情况下都为base64编码格式<br/>
 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
 * </p>
 * 
 */
public class rsautils{
 
  /**
   * 加密算法rsa
   */
  public static final string key_algorithm = "rsa";
   
  /**
   * 签名算法
   */
  public static final string signature_algorithm = "md5withrsa";
 
  /**
   * 获取公钥的key
   */
  private static final string public_key = "locatorpublickey";
   
  /**
   * 获取私钥的key
   */
  private static final string private_key = "locatorprivatekey";
   
  /**
   * rsa最大加密明文大小
   */
  private static final int max_encrypt_block = 117;
   
  /**
   * rsa最大解密密文大小
   */
  private static final int max_decrypt_block = 128;
 
  /**
   * <p>
   * 生成密钥对(公钥和私钥)
   * </p>
   * 
   * @return
   * @throws exception
   */
  public static map<string, object> genkeypair() throws exception {
    keypairgenerator keypairgen = keypairgenerator.getinstance(key_algorithm);
    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>
   * 用私钥对信息生成数字签名
   * </p>
   * 
   * @param data 已加密数据
   * @param privatekey 私钥(base64编码)
   * 
   * @return
   * @throws exception
   */
  public static string sign(byte[] data, string privatekey) throws exception {
    byte[] keybytes = base64utils.decode(privatekey);
    pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
    keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
    privatekey privatek = keyfactory.generateprivate(pkcs8keyspec);
    signature signature = signature.getinstance(signature_algorithm);
    signature.initsign(privatek);
    signature.update(data);
    return base64utils.encode(signature.sign());
  }
 
  /**
   * <p>
   * 校验数字签名
   * </p>
   * 
   * @param data 已加密数据
   * @param publickey 公钥(base64编码)
   * @param sign 数字签名
   * 
   * @return
   * @throws exception
   * 
   */
  public static boolean verify(byte[] data, string publickey, string sign)
      throws exception {
    byte[] keybytes = base64utils.decode(publickey);
    x509encodedkeyspec keyspec = new x509encodedkeyspec(keybytes);
    keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
    publickey publick = keyfactory.generatepublic(keyspec);
    signature signature = signature.getinstance(signature_algorithm);
    signature.initverify(publick);
    signature.update(data);
    return signature.verify(base64utils.decode(sign));
  }
 
  /**
   * <p>
   * 私钥解密
   * </p>
   * 
   * @param encrypteddata 已加密数据
   * @param privatekey 私钥(base64编码)
   * @return
   * @throws exception
   */
  public static byte[] decryptbyprivatekey(byte[] encrypteddata, string privatekey)
      throws exception {
    byte[] keybytes = base64utils.decode(privatekey);
    pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
    keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
    key privatek = keyfactory.generateprivate(pkcs8keyspec);
    cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
    cipher.init(cipher.decrypt_mode, privatek);
    int inputlen = encrypteddata.length;
    bytearrayoutputstream out = new bytearrayoutputstream();
    int offset = 0;
    byte[] cache;
    int i = 0;
    // 对数据分段解密
    while (inputlen - offset > 0) {
      if (inputlen - offset > max_decrypt_block) {
        cache = cipher.dofinal(encrypteddata, offset, max_decrypt_block);
      } else {
        cache = cipher.dofinal(encrypteddata, offset, inputlen - offset);
      }
      out.write(cache, 0, cache.length);
      i++;
      offset = i * max_decrypt_block;
    }
    byte[] decrypteddata = out.tobytearray();
    out.close();
    return decrypteddata;
  }
 
  /**
   * <p>
   * 公钥解密
   * </p>
   * 
   * @param encrypteddata 已加密数据
   * @param publickey 公钥(base64编码)
   * @return
   * @throws exception
   */
  public static byte[] decryptbypublickey(byte[] encrypteddata, 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);
    cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
    cipher.init(cipher.decrypt_mode, publick);
    int inputlen = encrypteddata.length;
    bytearrayoutputstream out = new bytearrayoutputstream();
    int offset = 0;
    byte[] cache;
    int i = 0;
    // 对数据分段解密
    while (inputlen - offset > 0) {
      if (inputlen - offset > max_decrypt_block) {
        cache = cipher.dofinal(encrypteddata, offset, max_decrypt_block);
      } else {
        cache = cipher.dofinal(encrypteddata, offset, inputlen - offset);
      }
      out.write(cache, 0, cache.length);
      i++;
      offset = i * max_decrypt_block;
    }
    byte[] decrypteddata = out.tobytearray();
    out.close();
    return decrypteddata;
  }
 
  /**
   * <p>
   * 公钥加密
   * </p>
   * 
   * @param data 源数据
   * @param publickey 公钥(base64编码)
   * @return
   * @throws exception
   */
  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
    cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
    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;
  }
 
  /**
   * <p>
   * 私钥加密
   * </p>
   * 
   * @param data 源数据
   * @param privatekey 私钥(base64编码)
   * @return
   * @throws exception
   */
  public static byte[] encryptbyprivatekey(byte[] data, string privatekey)
      throws exception {
    byte[] keybytes = base64utils.decode(privatekey);
    pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
    keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
    key privatek = keyfactory.generateprivate(pkcs8keyspec);
    cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
    cipher.init(cipher.encrypt_mode, privatek);
    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;
  }
 
  /**
   * <p>
   * 获取私钥
   * </p>
   * 
   * @param keymap 密钥对
   * @return
   * @throws exception
   */
  public static string getprivatekey(map<string, object> keymap)
      throws exception {
    key key = (key) keymap.get(private_key);
    return base64utils.encode(key.getencoded());
  }
 
  /**
   * <p>
   * 获取公钥
   * </p>
   * 
   * @param keymap 密钥对
   * @return
   * @throws exception
   */
  public static string getpublickey(map<string, object> keymap)
      throws exception {
    key key = (key) keymap.get(public_key);
    return base64utils.encode(key.getencoded());
  }
 
}

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