android RSA加密
這個RSA加密其實自己也沒有完全弄清楚，只是在網上自己找了一些資料，也是為了記錄自己的代碼。
概述
RSA是目前最有影響力的公鑰加密算法，該算法基于一個十分簡單的數論事實：將兩個大素數相乘十分容易，但那時想要對其乘積進行因式分解卻極其困 難，因此可以將乘積公開作為加密密鑰，即公鑰，而兩個大素數組合成私鑰。公鑰是可發布的供任何人使用，私鑰則為自己所有，供解密之用。關于RSA其它需要了解的知識，參考維基百科:http://zh.wikipedia.org/zh-cn/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95
在項目開發中對于一些比較敏感的信息需要對其進行加密處理，我們就可以使用RSA這種非對稱加密算法來對數據進行加密處理。
使用
秘鑰對的生成
1、我們可以在代碼里隨機生成密鑰對
?/**
? * 隨機生成RSA密鑰對
? *
? * @param keyLength
? *??????????? 密鑰長度，范圍：512～2048<br>
? *??????????? 一般1024
? * @return
? */
?public static KeyPair generateRSAKeyPair(int keyLength)
?{
??try
??{
???KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
???kpg.initialize(keyLength);
???return kpg.genKeyPair();
??} catch (NoSuchAlgorithmException e)
??{
???e.printStackTrace();
???return null;
??}
?}
其中KeyPair是android自帶的類，可以自帶生成RSA的私鑰 和 公鑰
package com.example.rsa;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigInteger;
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.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
/**
?* @author Mr.Zheng
?* @date 2014年8月22日 下午1:44:23
?*/
public final class RSAUtils
{
?private static String RSA = "RSA";
?/**
? * 隨機生成RSA密鑰對(默認密鑰長度為1024)
? *
? * @return
? */
?public static KeyPair generateRSAKeyPair()
?{
??return generateRSAKeyPair(1024);
?}
?/**
? * 隨機生成RSA密鑰對
? *
? * @param keyLength
? *??????????? 密鑰長度，范圍：512～2048<br>
? *??????????? 一般1024
? * @return
? */
?public static KeyPair generateRSAKeyPair(int keyLength)
?{
??try
??{
???KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
???kpg.initialize(keyLength);
???return kpg.genKeyPair();
??} catch (NoSuchAlgorithmException e)
??{
???e.printStackTrace();
???return null;
??}
?}
?/**
? * 用公鑰加密 <br>
? * 每次加密的字節數，不能超過密鑰的長度值減去11
? *
? * @param data
? *??????????? 需加密數據的byte數據
? * @param pubKey
? *??????????? 公鑰
? * @return 加密后的byte型數據
? */
?public static byte[] encryptData(byte[] data, PublicKey publicKey)
?{
??try
??{
???Cipher cipher = Cipher.getInstance(RSA);
???// 編碼前設定編碼方式及密鑰
???cipher.init(Cipher.ENCRYPT_MODE, publicKey);
???// 傳入編碼數據并返回編碼結果
???return cipher.doFinal(data);
??} catch (Exception e)
??{
???e.printStackTrace();
???return null;
??}
?}
?/**
? * 用私鑰解密
? *
? * @param encryptedData
? *??????????? 經過encryptedData()加密返回的byte數據
? * @param privateKey
? *??????????? 私鑰
? * @return
? */
?public static byte[] decryptData(byte[] encryptedData, PrivateKey privateKey)
?{
??try
??{
???Cipher cipher = Cipher.getInstance(RSA);
???cipher.init(Cipher.DECRYPT_MODE, privateKey);
???return cipher.doFinal(encryptedData);
??} catch (Exception e)
??{
???return null;
??}
?}
?/**
? * 通過公鑰byte[](publicKey.getEncoded())將公鑰還原，適用于RSA算法
? *
? * @param keyBytes
? * @return
? * @throws NoSuchAlgorithmException
? * @throws InvalidKeySpecException
? */
?public static PublicKey getPublicKey(byte[] keyBytes) throws NoSuchAlgorithmException,
???InvalidKeySpecException
?{
??X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
??KeyFactory keyFactory = KeyFactory.getInstance(RSA);
??PublicKey publicKey = keyFactory.generatePublic(keySpec);
??return publicKey;
?}
?/**
? * 通過私鑰byte[]將公鑰還原，適用于RSA算法
? *
? * @param keyBytes
? * @return
? * @throws NoSuchAlgorithmException
? * @throws InvalidKeySpecException
? */
?public static PrivateKey getPrivateKey(byte[] keyBytes) throws NoSuchAlgorithmException,
???InvalidKeySpecException
?{
??PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
??KeyFactory keyFactory = KeyFactory.getInstance(RSA);
??PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
??return privateKey;
?}
?/**
? * 使用N、e值還原公鑰
? *
? * @param modulus
? * @param publicExponent
? * @return
? * @throws NoSuchAlgorithmException
? * @throws InvalidKeySpecException
? */
?public static PublicKey getPublicKey(String modulus, String publicExponent)
???throws NoSuchAlgorithmException, InvalidKeySpecException
?{
??BigInteger bigIntModulus = new BigInteger(modulus);
??BigInteger bigIntPrivateExponent = new BigInteger(publicExponent);
??RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
??KeyFactory keyFactory = KeyFactory.getInstance(RSA);
??PublicKey publicKey = keyFactory.generatePublic(keySpec);
??return publicKey;
?}
?/**
? * 使用N、d值還原私鑰
? *
? * @param modulus
? * @param privateExponent
? * @return
? * @throws NoSuchAlgorithmException
? * @throws InvalidKeySpecException
? */
?public static PrivateKey getPrivateKey(String modulus, String privateExponent)
???throws NoSuchAlgorithmException, InvalidKeySpecException
?{
??BigInteger bigIntModulus = new BigInteger(modulus);
??BigInteger bigIntPrivateExponent = new BigInteger(privateExponent);
??RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
??KeyFactory keyFactory = KeyFactory.getInstance(RSA);
??PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
??return privateKey;
?}
?/**
? * 從字符串中加載公鑰
? *
? * @param publicKeyStr
? *??????????? 公鑰數據字符串
? * @throws Exception
? *???????????? 加載公鑰時產生的異常
? */
?public static PublicKey loadPublicKey(String publicKeyStr) throws Exception
?{
??try
??{
???byte[] buffer = Base64Utils.decode(publicKeyStr);
???KeyFactory keyFactory = KeyFactory.getInstance(RSA);
???X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
???return (RSAPublicKey) keyFactory.generatePublic(keySpec);
??} catch (NoSuchAlgorithmException e)
??{
???throw new Exception("無此算法");
??} catch (InvalidKeySpecException e)
??{
???throw new Exception("公鑰非法");
??} catch (NullPointerException e)
??{
???throw new Exception("公鑰數據為空");
??}
?}
?/**
? * 從字符串中加載私鑰<br>
? * 加載時使用的是PKCS8EncodedKeySpec（PKCS#8編碼的Key指令）。
? *
? * @param privateKeyStr
? * @return
? * @throws Exception
? */
?public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception
?{
??try
??{
???byte[] buffer = Base64Utils.decode(privateKeyStr);
???// X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
???PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
???KeyFactory keyFactory = KeyFactory.getInstance(RSA);
???return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
??} catch (NoSuchAlgorithmException e)
??{
???throw new Exception("無此算法");
??} catch (InvalidKeySpecException e)
??{
???throw new Exception("私鑰非法");
??} catch (NullPointerException e)
??{
???throw new Exception("私鑰數據為空");
??}
?}
?/**
? * 從文件中輸入流中加載公鑰
? *
? * @param in
? *??????????? 公鑰輸入流
? * @throws Exception
? *???????????? 加載公鑰時產生的異常
? */
?public static PublicKey loadPublicKey(InputStream in) throws Exception
?{
??try
??{
???return loadPublicKey(readKey(in));
??} catch (IOException e)
??{
???throw new Exception("公鑰數據流讀取錯誤");
??} catch (NullPointerException e)
??{
???throw new Exception("公鑰輸入流為空");
??}
?}
?/**
? * 從文件中加載私鑰
? *
? * @param keyFileName
? *??????????? 私鑰文件名
? * @return 是否成功
? * @throws Exception
? */
?public static PrivateKey loadPrivateKey(InputStream in) throws Exception
?{
??try
??{
???return loadPrivateKey(readKey(in));
??} catch (IOException e)
??{
???throw new Exception("私鑰數據讀取錯誤");
??} catch (NullPointerException e)
??{
???throw new Exception("私鑰輸入流為空");
??}
?}
?/**
? * 讀取密鑰信息
? *
? * @param in
? * @return
? * @throws IOException
? */
?private static String readKey(InputStream in) throws IOException
?{
??BufferedReader br = new BufferedReader(new InputStreamReader(in));
??String readLine = null;
??StringBuilder sb = new StringBuilder();
??while ((readLine = br.readLine()) != null)
??{
???if (readLine.charAt(0) == '-')
???{
????continue;
???} else
???{
????sb.append(readLine);
????sb.append('\r');
???}
??}
??return sb.toString();
?}
?/**
? * 打印公鑰信息
? *
? * @param publicKey
? */
?public static void printPublicKeyInfo(PublicKey publicKey)
?{
??RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
??System.out.println("----------RSAPublicKey----------");
??System.out.println("Modulus.length=" + rsaPublicKey.getModulus().bitLength());
??System.out.println("Modulus=" + rsaPublicKey.getModulus().toString());
??System.out.println("PublicExponent.length=" + rsaPublicKey.getPublicExponent().bitLength());
??System.out.println("PublicExponent=" + rsaPublicKey.getPublicExponent().toString());
?}
?public static void printPrivateKeyInfo(PrivateKey privateKey)
?{
??RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
??System.out.println("----------RSAPrivateKey ----------");
??System.out.println("Modulus.length=" + rsaPrivateKey.getModulus().bitLength());
??System.out.println("Modulus=" + rsaPrivateKey.getModulus().toString());
??System.out.println("PrivateExponent.length=" + rsaPrivateKey.getPrivateExponent().bitLength());
??System.out.println("PrivatecExponent=" + rsaPrivateKey.getPrivateExponent().toString());
?}
}
這個是建立了一個工具類，所以可以直接使用加密。
代碼中有些需要使用Base64再轉換的，而java中不自帶，Android中自帶，所以自己寫出一個來，方便Java后臺使用package com.example.rsa;
import java.io.UnsupportedEncodingException;
/**
?* @author Mr.Zheng
?* @date 2014年8月22日 下午9:50:28
?*/
public class Base64Utils
{
?private static char[] base64EncodeChars = new char[]
?{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
???'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
???'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
???'6', '7', '8', '9', '+', '/' };
?private static byte[] base64DecodeChars = new byte[]
?{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
???-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
???54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
???12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
???30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1,
???-1, -1, -1 };
?/**
? * 加密
? *
? * @param data
? * @return
? */
?public static String encode(byte[] data)
?{
??StringBuffer sb = new StringBuffer();
??int len = data.length;
??int i = 0;
??int b1, b2, b3;
??while (i < len)
??{
???b1 = data[i++] & 0xff;
???if (i == len)
???{
????sb.append(base64EncodeChars[b1 >>> 2]);
????sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
????sb.append("==");
????break;
???}
???b2 = data[i++] & 0xff;
???if (i == len)
???{
????sb.append(base64EncodeChars[b1 >>> 2]);
????sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
????sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
????sb.append("=");
????break;
???}
???b3 = data[i++] & 0xff;
???sb.append(base64EncodeChars[b1 >>> 2]);
???sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
???sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
???sb.append(base64EncodeChars[b3 & 0x3f]);
??}
??return sb.toString();
?}
?/**
? * 解密
? *
? * @param str
? * @return
? */
?public static byte[] decode(String str)
?{
??try
??{
???return decodePrivate(str);
??} catch (UnsupportedEncodingException e)
??{
???e.printStackTrace();
??}
??return new byte[]
??{};
?}
?private static byte[] decodePrivate(String str) throws UnsupportedEncodingException
?{
??StringBuffer sb = new StringBuffer();
??byte[] data = null;
??data = str.getBytes("US-ASCII");
??int len = data.length;
??int i = 0;
??int b1, b2, b3, b4;
??while (i < len)
??{
???do
???{
????b1 = base64DecodeChars[data[i++]];
???} while (i < len && b1 == -1);
???if (b1 == -1)
????break;
???do
???{
????b2 = base64DecodeChars[data[i++]];
???} while (i < len && b2 == -1);
???if (b2 == -1)
????break;
???sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
???do
???{
????b3 = data[i++];
????if (b3 == 61)
?????return sb.toString().getBytes("iso8859-1");
????b3 = base64DecodeChars[b3];
???} while (i < len && b3 == -1);
???if (b3 == -1)
????break;
???sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
???do
???{
????b4 = data[i++];
????if (b4 == 61)
?????return sb.toString().getBytes("iso8859-1");
????b4 = base64DecodeChars[b4];
???} while (i < len && b4 == -1);
???if (b4 == -1)
????break;
???sb.append((char) (((b3 & 0x03) << 6) | b4));
??}
??return sb.toString().getBytes("iso8859-1");
?}
}
最后直接使用和加密就可以了，文章參考了別人的博客，如果看不懂，那建議去網上再搜索一下。
總結
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