SHA1WithRSA签名

/**  
 * @Title:  RSA.java   
 * @Package com.rsa   
 * @Description:    描述   
 * @author: xu_yuxin    
 * @date:   2019年11月27日 下午3:44:30   
 * @version V1.0 
 * @Copyright: 
 */
package com.rsa;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;

public class RSA {

	public static final String SIGN_ALGORITHMS = "SHA1WithRSA";

	/**
	 * RSA签名
	 * 
	 * @param content       待签名数据
	 * @param privateKey    商户私钥
	 * @param input_charset 编码格式
	 * @return 签名值
	 */
	public static String sign(String content, String privateKey, String input_charset) {
		try {
			PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(Base64.decode(privateKey));
			KeyFactory keyf = KeyFactory.getInstance("RSA");
			PrivateKey priKey = keyf.generatePrivate(priPKCS8);

			java.security.Signature signature = java.security.Signature.getInstance(SIGN_ALGORITHMS);

			signature.initSign(priKey);
			signature.update(content.getBytes(input_charset));

			byte[] signed = signature.sign();

			return Base64.encode(signed);
		} catch (Exception e) {
			e.printStackTrace();
		}

		return null;
	}

	/**
	 * RSA验签名检查
	 * 
	 * @param content        待签名数据
	 * @param sign           签名值
	 * @param ali_public_key 支付宝公钥
	 * @param input_charset  编码格式
	 * @return 布尔值
	 */
	public static boolean verify(String content, String sign, String ali_public_key, String input_charset) {
		try {
			KeyFactory keyFactory = KeyFactory.getInstance("RSA");
			byte[] encodedKey = Base64.decode(ali_public_key);
			PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));

			java.security.Signature signature = java.security.Signature.getInstance(SIGN_ALGORITHMS);

			signature.initVerify(pubKey);
			signature.update(content.getBytes(input_charset));

			boolean bverify = signature.verify(Base64.decode(sign));
			return bverify;

		} catch (Exception e) {
			e.printStackTrace();
		}

		return false;
	}

	/**
	 * 解密
	 * 
	 * @param content       密文
	 * @param private_key   商户私钥
	 * @param input_charset 编码格式
	 * @return 解密后的字符串
	 */
	public static String decrypt(String content, String private_key, String input_charset) throws Exception {
		PrivateKey prikey = getPrivateKey(private_key);

		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, prikey);

		InputStream ins = new ByteArrayInputStream(Base64.decode(content));
		ByteArrayOutputStream writer = new ByteArrayOutputStream();
		//rsa解密的字节大小最多是128，将需要解密的内容，按128位拆开解密
		byte[] buf = new byte[128];
		int bufl;

		while ((bufl = ins.read(buf)) != -1) {
			byte[] block = null;

			if (buf.length == bufl) {
				block = buf;
			} else {
				block = new byte[bufl];
				for (int i = 0; i < bufl; i++) {
					block[i] = buf[i];
				}
			}

			writer.write(cipher.doFinal(block));
		}

		return new String(writer.toByteArray(), input_charset);
	}

	/**
	 * 得到私钥
	 * 
	 * @param key 密钥字符串（经过base64编码）
	 * @throws Exception
	 */
	public static PrivateKey getPrivateKey(String key) throws Exception {

		byte[] keyBytes;

		keyBytes = Base64.decode(key);

		PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

		KeyFactory keyFactory = KeyFactory.getInstance("RSA");

		PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

		return privateKey;
	}
}