Android RSA公鑰加密

參考：http://www.bkjia.com/Androidjc/868958.html

利用OpenSSL工具生成密鑰對，參考以上文章時利用公鑰加密後的，後臺始終無法解密（不知道哪錯了，還是不用自定義的Base64吧）。

最後使用以下方法加密成功：

RSAUtil.encryptByPublic(Context context, String content)

下面的"public_key.pem"即爲公鑰。

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import android.content.Context;
import android.util.Base64;

/**
 * RSA加密工具
 * 
 * @author Administrator
 * 
 */
public class RSAUtil
{
	public static final String RSA_PUBLIC = "";
	
	/**
	 * 得到公鑰
	 * 
	 * @param algorithm
	 * @param bysKey
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws Exception
	 */
	private static PublicKey getPublicKeyFromX509(String algorithm,
			String bysKey) throws NoSuchAlgorithmException, Exception
	{
		byte[] decodeKey = Base64.decode(bysKey, Base64.DEFAULT);
		X509EncodedKeySpec x509 = new X509EncodedKeySpec(decodeKey);
		KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
		return keyFactory.generatePublic(x509);
	}

	/**
	 * 使用公鑰加密
	 * 
	 * @param content
	 * @return
	 */
	public static String encryptByPublic(Context context, String content)
	{
		try
		{
			String pubKey = getPublicKeyFromAssets(context);
			PublicKey publicKey = getPublicKeyFromX509(ALGORITHM, pubKey);
			Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
			cipher.init(Cipher.ENCRYPT_MODE, publicKey);
			byte[] plaintext = content.getBytes();
			byte[] output = cipher.doFinal(plaintext);

			String str = Base64.encodeToString(output, Base64.DEFAULT);
			return str;
		} catch (Exception e)
		{
			e.printStackTrace();
			return null;
		}
	}


	/**
	 * 獲取公鑰
	 * 
	 * @param fileName
	 * @return
	 */
	private static String getPublicKeyFromAssets(Context context)
	{
		try
		{
			InputStreamReader inputReader = new InputStreamReader(context
					.getResources().getAssets().open("public_key.pem"));
			BufferedReader bufReader = new BufferedReader(inputReader);
			String line = "";
			String Result = "";
			while ((line = bufReader.readLine()) != null)
			{
				if (line.charAt(0) == '-')
				{
					continue;
				}
				Result += line;
			}
			return Result;
		} catch (Exception e)
		{
			e.printStackTrace();
			return null;
		}
	}
}

android、ios客戶端rsa加密祕鑰生成 http://sparrow82.iteye.com/blog/1834859

1、openssl生成公司鑰對 
openssl req -x509 -out public_key.der -outform der -new -newkey rsa:1024 -keyout private_key.pem 

生成私鑰：private_key.pem 
公鑰：public_key.der 

2、將private_key.pem轉換成PKCS8Padding格式 
openssl pkcs8 -topk8 -inform PEM -in private_key.pem -outform PEM -nocrypt 
返回一串字符如： 
-----BEGIN PRIVATE KEY----- 
MIICdgIBADANBgkqhkiG9w0BAQEFAASCAmAwggJcAgEAAoGBAKwerXN6yQc0hOyP 
aqQkTA0kANym5cLgoTUvCk3b3DDn2fQvfXjLqPx/lzYDRIQljO9wqOEL8bpTas6C 
ymN7Ioq/a0uNpYOimp7inlfYiwr/3ju1ZBtg7w9WDZUMivlPuEATbsj5Z0ZUMeyk 
7Mi2vW2hGx0rROVbiXpx7u6bu54BAgMBAAECgYEApAB/KV+/mPv0BCwLYuerB4Jc 
x+LHXs8HDFQML2/k+TySMtflaGo2VJGGlVK7wGa/SY9Be14UMIQ3axq4md3EZHuy 
ibnFfPJHHfSubGxpg+IRUvtuUExTpZ9GT4y6depEWGllmR4CHZVt100tkOYAeDsl 
suE3UmYHTHr20tqJ/BkCQQDdc1+qIV/VM+S49yYoFWvAt/bF80HyNMJJZLwcwzP2 
NC/i8QS8AqtbkayLTsKGMc+Naw2UE7a7hOH4UwWmFb9rAkEAxvkOJsSuGv9FK7nV 
k83NT5NURdAXTNlu4AYmTIdCA4XW8+I0BxoPmuNhqbZuus8i0D4LWREb4F2YNiqM 
2onPQwJARO6U6LBa1FLC75B/IBsK34JkHloKPQqPL6lbpNheZFT6UvoTLzLlhCtk 
OjjZ9Eus/6hDIcTBLL3AWTv+liRO4QJAMFlSo/8E45CGCWMFz/2hVyXQw4oWL1li 
hNNZuRzg4KREIE0mIVem1RdNowSukXxF1F5POZxbrsBvfTIHug7kqwJABumKLTAs 
tRKj4mXmH9tyUFCOrwRDqY/XIC9NLu+l7X1WfdgbSi++OQ0qa2LV6dHQhHNdEYmt 
sh2JnjcySwHROg== 
-----END PRIVATE KEY----- 
取出-----BEGIN PRIVATE KEY-----和-----END PRIVATE KEY-----之間的字符保存，做爲解密的私鑰串。 

3、將生成的公鑰DER文件BASE64編碼 
openssl base64 -in public_key.der 
生成的字符串做爲IOS的公鑰 

4、從已有的私鑰中，導出android使用的公鑰 
openssl rsa -in private_key.pem -pubout -out rsa_public_key.pem