java
import com.tratao.jcommon.common.BaseServiceException;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.io.IOUtils;
import org.springframework.stereotype.Component;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class RsaUtil {

	public static final String CHARSET = "UTF-8";
	public static final String RSA_ALGORITHM = "RSA";
	public static final String RSA_ALGORITHM_SIGN = "SHA256WithRSA";
	
	/**
	* sign data
	* @param data the string value
	* @param privateKeyStr private key 
	* @return
	*/
	public String sign(String data,String privateKeyStr){
	  try{
	      //sign
	      KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
	      PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyStr));
	      privateKey = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
	      Signature signature = Signature.getInstance(RSA_ALGORITHM_SIGN);
	      signature.initSign(privateKey);
	      signature.update(data.getBytes(CHARSET));
	      return Base64.encodeBase64URLSafeString(signature.sign());
	  }catch(Exception e){
	      throw new RuntimeException("sign data: [" + data + "] throw exception", e);
	  }
	}
	
	/**
	 * decrypt data
	 * @param data sign data
	 * @param privateKeyStr private key
	 * @return
	 */
	public String privateDecrypt(String data,String privateKeyStr){
	    try{
	        KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
	        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyStr));
	        privateKey = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
	        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
	        cipher.init(Cipher.DECRYPT_MODE, privateKey);
	        return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), privateKey.getModulus().bitLength()), CHARSET);
	    } catch(Exception e){
	        throw new RuntimeException("decrypt sign data: [" + data + "] throw exception", e);
	    }
	}
}