android上的MD5和RSA的加解密

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {
	/*
	 * MD5加密
	 */
	public static String getDigest(String str) {
		MessageDigest messageDigest = null;

		try {
			messageDigest = MessageDigest.getInstance("MD5");
			messageDigest.reset();
			messageDigest.update(str.getBytes("UTF-8"));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}

		byte[] byteArray = messageDigest.digest();
		StringBuffer md5StrBuff = new StringBuffer();

		for (int i = 0; i < byteArray.length; i++) {
			if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
				md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
			else
				md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
		}
		return md5StrBuff.toString().toUpperCase();
	}
}

import java.math.BigInteger;
import java.security.Key;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.spec.RSAPublicKeySpec;

import javax.crypto.Cipher;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

public class RSAUtil {
	/**
	 * 加密
	 * 
	 * @param message
	 * @return
	 */
	public static String encrypt(String message) {
		byte[] result = null;

		try {
			result = encrypt(message, getPublicKey());
		} catch (Exception e) {
			e.printStackTrace();
		}

		return toHexString(result);
	}

	/**
	 * 解密
	 * 
	 * @param message
	 * @return
	 */
	public static String decrypt(String message) {
		byte[] result = null;

		try {
			result = decrypt(message, getPublicKey());
		} catch (Exception e) {
			e.printStackTrace();
		}

		return new String(result);
	}

	/**
	 * 加密(公钥加密、私钥加密)
	 * 
	 * @param message 待加密的消息
	 * @param key 公钥或私钥
	 * @return
	 * @throws Exception
	 */
	private static byte[] encrypt(String message, Key key) throws Exception {
		Cipher cipher = Cipher.getInstance("RSA", new BouncyCastleProvider());
		cipher.init(Cipher.ENCRYPT_MODE, key);

		// 注意中文的处理
		return cipher.doFinal(message.getBytes("gb2312"));
	}

	/**
	 * 解密(如果公钥加密，则用私钥解密；如果私钥加密，则用公钥解密)
	 * 
	 * @param message 待解密的消息
	 * @param key 公钥或私钥
	 * @return
	 * @throws Exception
	 */
	private static byte[] decrypt(String message, Key key) throws Exception {
		Cipher cipher = Cipher.getInstance("RSA", new BouncyCastleProvider());
		cipher.init(Cipher.DECRYPT_MODE, key);
		return cipher.doFinal(toBytes(message));
	}

	/**
	 * 通过模长和公钥指数获取公钥
	 * 
	 * @param modulus 模长
	 * @param publicExponent 公钥指数
	 * @return
	 * @throws Exception
	 */
	public static PublicKey getPublicKey() {
		PublicKey publicKey = null;
		String modulus = "140865665237544398577638791993321201143991791099370252934699963963887058026979531275917645451893685346013654333931757603593193739776986525943697469996693704995753266331593233395038088698299308180612215713544577462613426793519824197226393059683065343801412208205295045502348474411031999124137863144916358656019";
		String publicExponent = "65537";
		BigInteger m = new BigInteger(modulus);
		BigInteger e = new BigInteger(publicExponent);
		RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e);

		try {
			KeyFactory keyFactory = KeyFactory.getInstance("RSA", new BouncyCastleProvider());
			publicKey = keyFactory.generatePublic(keySpec);
		} catch (Exception e1) {
			e1.printStackTrace();
		}

		return publicKey;
	}

	private static final byte[] toBytes(String s) {
		byte[] bytes;
		bytes = new byte[s.length() / 2];
		for (int i = 0; i < bytes.length; i++) {
			bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2), 16);
		}
		return bytes;
	}

	public static String toHexString(byte[] b) {
		StringBuilder sb = new StringBuilder(b.length * 2);
		for (int i = 0; i < b.length; i++) {
			sb.append(HEXCHAR[(b[i] & 0xf0) >>> 4]);
			sb.append(HEXCHAR[b[i] & 0x0f]);
		}
		return sb.toString();
	}

	private static char[] HEXCHAR = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
}

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends Activity {
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		String info = "不知道什么时候，开始喜欢这里，每个夜里都会来这里看你。";
		Log.d("zhangxy",MD5.getDigest(info));
		// 公钥加密
		Log.d("zhangxy",RSAUtil.encrypt(info));
		// 公钥解密（经私钥加密）
		Log.d("zhangxy", RSAUtil.decrypt("94d5ffca913465785714348f10c57c8a0226aca2c8a5294d3a32f398c4791bee8bb37873e16a7b71ed64e40ac121ec4f4bf375b881421a17a3f10789dc543ab41c26c11ba1184b2e0328ef6d354e191f7d978bd9b984e76d310e028b3412093f7296d58d9adb7f9e4b5eb6427c369ae5e919f848c7a21b7794d5985e4d3ad10a"));
	}
}