【java】加密方式

/**
 * String Utility Class This is used to encode passwords programmatically
 * 
 * <p>
 * <a h ref="StringUtil.java.html"><i>View Source</i></a>
 * </p>
 * 
 * @author <a href="mailto:[e-mail]">Matt Raible</a>
 */
public class PasswordMD5Encryption {
	// ~ Static fields/initializers
	private static Logger logger  = Logger.getLogger(PasswordMD5Encryption.class);
	private final static Log log = LogFactory
			.getLog(PasswordMD5Encryption.class);

	// ~ Methods
	/**
	 * Encode a string using algorithm specified in web.xml and return the
	 * resulting encrypted password. If exception, the plain credentials string
	 * is returned
	 * 
	 * @param password
	 *            Password or other credentials to use in authenticating this
	 *            username
	 * @param algorithm
	 *            Algorithm used to do the digest
	 * 
	 * @return encypted password based on the algorithm.
	 */
	public static String encodePassword(String password, String algorithm) {
		byte[] unencodedPassword = password.getBytes();

		MessageDigest md = null;

		try {
			// first create an instance, given the provider
			md = MessageDigest.getInstance(algorithm);
		} catch (Exception e) {
			log.error("Exception: " + e);

			return password;
		}

		md.reset();

		// call the update method one or more times
		// (useful when you don't know the size of your data, eg. stream)
		md.update(unencodedPassword);

		// now calculate the hash
		byte[] encodedPassword = md.digest();

		StringBuffer buf = new StringBuffer();

		for (int i = 0; i < encodedPassword.length; i++) {
			if ((encodedPassword[i] & 0xff) < 0x10) {
				buf.append("0");
			}

			buf.append(Long.toString(encodedPassword[i] & 0xff, 16));
		}

		return buf.toString();
	}

	/**
	 * Encode a string using Base64 encoding. Used when storing passwords as
	 * cookies.
	 * 
	 * This is weak encoding in that anyone can use the decodeString routine to
	 * reverse the encoding.
	 * 
	 * @param str
	 * @return String
	 */
	public static String encodeString(String str) {
		sun.misc.BASE64Encoder encoder = new sun.misc.BASE64Encoder();
		return encoder.encodeBuffer(str.getBytes()).trim();
	}

	/**
	 * Decode a string using Base64 encoding.
	 * @param str
	 * @return String
	 */
	public static String decodeString(String str) {
		sun.misc.BASE64Decoder dec = new sun.misc.BASE64Decoder();
		try {
			return new String(dec.decodeBuffer(str));
		} catch (IOException io) {
			throw new RuntimeException(io.getMessage(), io.getCause());
		}
	}
	
	public static void main(String[] args) {
                String passString = "123456";
		String newpass = PasswordMD5Encryption.encodeString(passString);
		System.out.println(passString+" 加密后的字符串是 : " + newpass);
		String newpassAgin = PasswordMD5Encryption.decodeString(newpass);
		System.out.println(newpass+" 加密后再解密的字符串是 : " + newpassAgin);
	}
}

 

 

1. MD5加密，常用于加密用户名密码，当用户验证时。 不可逆

protected byte[] encrypt(byte[] obj) ...{
    try ...{
        MessageDigest md5 = MessageDigest.getInstance("MD5");
            md5.update(obj);
        return md5.digest();
    } catch (NoSuchAlgorithmException e) ...{
        e.printStackTrace();
    }
}

2. SHA加密，与MD5相似的用法，只是两者的算法不同。

protected byte[] encrypt(byte[] obj) ...{
    try ...{
        MessageDigest sha = MessageDigest.getInstance("SHA");
            sha.update(obj);
        return sha.digest();
    } catch (NoSuchAlgorithmException e) ...{
        e.printStackTrace();
    }
}

3. RSA加密，RAS加密允许解密。常用于文本内容的加密。

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;

import javax.crypto.Cipher;

/** *//**
 * <b>RSAEncrypt</b>
 * <p>
 * @author maqujun
 * @see
 */
public class RSAEncrypt ...{

    /** *//**
 * Main method for RSAEncrypt.
     * @param args
     */
    public static void main(String[] args) ...{
        try ...{
            RSAEncrypt encrypt = new RSAEncrypt();
            
            String encryptText = "encryptText";
            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
            keyPairGen.initialize(1024);
            KeyPair keyPair = keyPairGen.generateKeyPair();
            // Generate keys
            RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
            RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
            
            byte[] e = encrypt.encrypt(publicKey, encryptText.getBytes());
            byte[] de = encrypt.decrypt(privateKey,e);
            System.out.println(encrypt.bytesToString(e));
            System.out.println(encrypt.bytesToString(de));
        } catch (Exception e) ...{
            e.printStackTrace();
        }
    }
    
/** *//**
     * Change byte array to String.
     * @return byte[]
     */
    protected String bytesToString(byte[] encrytpByte) ...{
        String result = "";
        for (Byte bytes : encrytpByte) ...{
            result += (char) bytes.intValue();
        }
        return result;
    }
    
/** *//**
     * Encrypt String.
     * @return byte[]
     */
    protected byte[] encrypt(RSAPublicKey publicKey, byte[] obj)  ...{
        if (publicKey != null) ...{
            try ...{
                Cipher cipher = Cipher.getInstance("RSA");
                cipher.init(Cipher.ENCRYPT_MODE, publicKey);
                return cipher.doFinal(obj);
            } catch (Exception e) ...{
                e.printStackTrace();
            }
        }
        return null;
    }

    /** *//**
     * Basic decrypt method
     * @return byte[]
     */
    protected byte[] decrypt(RSAPrivateKey privateKey, byte[] obj) ...{
        if (privateKey != null) ...{
                try ...{
                    Cipher cipher = Cipher.getInstance("RSA");
                    cipher.init(Cipher.DECRYPT_MODE, privateKey);
                    return cipher.doFinal(obj);
                } catch (Exception e) ...{
                    e.printStackTrace();
                }
            }
    
        return null;
    }
}

学习网址：http://www.ibm.com/developerworks/cn/java/l-security/

 

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