RSA 암복호화

결제 관련 API 연동(VAN, PG, 간편결제 등) 할 경우 RSA암복호화 과정을 거치게되는데

이 부분에 대한 샘플 코드를 작성해 보았다.

 

Apache Commons Codec 다운로드

commons.apache.org/proper/commons-codec/

Codec – Home

 

프로젝트 라이브러리에 추가. 

 

PublicKey와 PrivateKey 파일을 생성

package com.ubpay.keypair;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;

//
// RSA Key 파일 생성
//
// Created by netcanis on 2019/04/29.
// Copyright © 2019 netcanis. All rights reserved.
//

// Download Apache Commons Codec
// https://commons.apache.org/proper/commons-codec/download_codec.cgi

public class GenKeys
{
	private KeyPairGenerator keyGen;
	private KeyPair pair;
	private PrivateKey privateKey;
	private PublicKey publicKey;

	// RSA 초기화 및 키 생성 
	public GenKeys(int keysize) throws NoSuchAlgorithmException, NoSuchProviderException {
		this.keyGen = KeyPairGenerator.getInstance("RSA");
		this.keyGen.initialize(keysize);
		this.pair = this.keyGen.generateKeyPair();
		this.publicKey = pair.getPublic();
		this.privateKey = pair.getPrivate();
	}

	public PublicKey getPublicKey() {
		return this.publicKey;
	}
	
	public PrivateKey getPrivateKey() {
		return this.privateKey;
	}
	
	public void writeToFile(String path, byte[] key) throws IOException {
		File f = new File(path);
		f.getParentFile().mkdirs();

		FileOutputStream fos = new FileOutputStream(f);
		fos.write(key);
		fos.flush();
		fos.close();
	}

	
	
	public static void main(String[] args) {
		GenKeys genKeys;
		try {
			// 1024bit key pair 생성  
			genKeys = new GenKeys(1024);
			
			System.out.println(genKeys.publicKey);
			System.out.println(genKeys.privateKey);
			
			// 바이너리 파일로 저장 
			genKeys.writeToFile("KeyPair/public.key", genKeys.getPublicKey().getEncoded());
			genKeys.writeToFile("KeyPair/private.key", genKeys.getPrivateKey().getEncoded());
			
		} catch (NoSuchAlgorithmException | NoSuchProviderException e) {
			System.err.println(e.getMessage());
		} catch (IOException e) {
			System.err.println(e.getMessage());
		}
	}
}

 

생성 결과

 

생성된 키를 이용하여 암복호화 테스트

package com.ubpay.rsaTest;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.file.Files;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.DSAPrivateKeySpec;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.EncodedKeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import org.apache.commons.codec.binary.Base64;


//
// RSA 암복호화 및 테스트
//
// Created by netcanis on 2019/04/29.
// Copyright © 2019 netcanis. All rights reserved.
//

public class RSAEncryption
{
	private Cipher cipher;
	
	public RSAEncryption() throws NoSuchAlgorithmException, NoSuchPaddingException{
		this.cipher = Cipher.getInstance("RSA");
	}
	
	// 주어진 파일을 byte array로 읽기 
	public byte[] getFileInBytes(File f) throws IOException{
		FileInputStream fis = new FileInputStream(f);
		byte[] fbytes = new byte[(int) f.length()];
		fis.read(fbytes);
		fis.close();
		return fbytes;
	}
		
	// X509EncodedKey
	public PublicKey getPublic(String filename) throws Exception {
		byte[] keyBytes = Files.readAllBytes(new File(filename).toPath());
		X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
		KeyFactory kf = KeyFactory.getInstance("RSA");
		return kf.generatePublic(spec);
	}

	// PKCS8EncodedKeySpec
	public PrivateKey getPrivate(String filename) throws Exception {
		byte[] keyBytes = Files.readAllBytes(new File(filename).toPath());
		
		//byte[] decoded = Base64.getDecoder().decode(keyBytes);
		//println(new String(decoded));    // Outputs "Hello"
		
		//Base64 codec = new Base64();
		//byte[] decoded = codec.decode(keyBytes);
		//System.out.println( new String(decoded) );    // Outputs "Hello"
		
		PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory kf = KeyFactory.getInstance("RSA");
		return kf.generatePrivate(spec);
	}
	
	// public key로 암호화 
	public String encrypt(String str, PublicKey key) throws NoSuchAlgorithmException, NoSuchPaddingException, UnsupportedEncodingException, IllegalBlockSizeException, BadPaddingException, InvalidKeyException{
		this.cipher.init(Cipher.ENCRYPT_MODE, key);
		return Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
	}
	
	// private key로 복호화 
	public String decrypt(String str, PrivateKey key) throws InvalidKeyException, UnsupportedEncodingException, IllegalBlockSizeException, BadPaddingException{
		this.cipher.init(Cipher.DECRYPT_MODE, key);
		return new String(cipher.doFinal(Base64.decodeBase64(str)), "UTF-8");
	}

	// hex to byte[]
	public byte[] hexStringToByteArray(String s) {
	    int len = s.length();
	    byte[] data = new byte[len / 2];
	    for (int i = 0; i < len; i += 2) {
	        data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
	                             + Character.digit(s.charAt(i+1), 16));
	    }
	    return data;
	}
	
	// byte[] to hex
	public String byteArrayToHexString(byte[] bytes){ 
		StringBuilder sb = new StringBuilder(); 
		for(byte b : bytes){ 
			sb.append(String.format("%02X", b&0xff)); 
		} 
		return sb.toString(); 
	} 

	
    
	public static void main(String[] args) throws Exception {
		RSAEncryption ac = new RSAEncryption();
		
		// 공개키
		PublicKey publicKey = ac.getPublic("KeyPair/public.key");
		// 개인키 
		PrivateKey privateKey = ac.getPrivate("KeyPair/private.key");
		
		// 원문 
		String msg = "test message";
		
		
		System.out.println("----------------------------------------------------");
		System.out.println(":::: TEST 암호화 및 복호화 ::::");
		
		// 암호화 원문 BASE64
		String encryptedString = ac.encrypt(msg, publicKey);
		// 복호화
		String decryptedString = ac.decrypt(encryptedString, privateKey);
		
		System.out.println("----------------------------------------------------");
		System.out.println(
				"원문 = " + msg + "\n" +
				"공개키 암호화 = " + encryptedString + "\n" +
				"개인키 복호화 = " + decryptedString
				);
		System.out.println("----------------------------------------------------");
	}
}




결과 :
--------------------------------------------------------------------------
:::: TEST 암호화 및 복호화 ::::
--------------------------------------------------------------------------
원문 = test message
공개키 암호화 = gz2WQHCyHxsPV5IB0xehk8RSbGrhGR86nQRGj09CphxiIAjRsCony8myWfRGJgDVyK6ixuK13gtL/20j4K5c1GcCKxPT9xqYaa6tBxTakho9klHNAO6KhQJK0nGeIQRDpZ1qecB6pPMsRqVVO5rb81NFqbjLKMoqi2tO1f55/iM=
개인키 복호화 = test message
--------------------------------------------------------------------------

 

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