웹에서 javascirpt 와 java 간의 서로 사용 방법으로 해도 될것 같습니다.
일단 대표적인 2가지를 알아 보겠습니다.
여기에서 보통 JAVA 에서 지원 되는 라이브러리는 PKCS#8이 대부분이고 예제 대부분이 또한 PKCS#8 입니다.
PKCS#1 입니다.
java 에서 난감하게 됩니다 .
그래서 PKCS#1을 java 에서 읽을수 있는 방법을 기록 합니다.
MAVEN 에 해당 라이브러리 추가 필요 합니다.
package apitest.com;
import java.io.IOException;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import sun.security.util.DerInputStream;
import sun.security.util.DerValue;
public class MainA {
public static void main(String[] args) throws IOException, GeneralSecurityException {
// TODO Auto-generated method stub
String sPublicKey2 = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCMZXFISQhUtIXT8dQGC6KX/fnV" +
"/bxCLYPJXAc/1xlgLyurlqusivW6AzYlQYsmAX7v50JyvYxeOxdDKkcz+tU8BhLY" +
"beZSJZ9tkrtYsem+knegRKujKbKWTm3GIPPK1hiifhc9fC+lGKv2199VHBjcFtZc" +
"hmq14ef17FFJqDVEyQIDAQAB";
String sPrivateKey2 = "MIICXQIBAAKBgQCMZXFISQhUtIXT8dQGC6KX/fnV/bxCLYPJXAc/1xlgLyurlqus" +
"ivW6AzYlQYsmAX7v50JyvYxeOxdDKkcz+tU8BhLYbeZSJZ9tkrtYsem+knegRKuj" +
"KbKWTm3GIPPK1hiifhc9fC+lGKv2199VHBjcFtZchmq14ef17FFJqDVEyQIDAQAB" +
"AoGAZwbmS7J0b5yN/Mug2NLe/YS+Oz/ZUAMQi8qB82JI1+GlvWRzFMpgqqFCsbJY" +
"h4pfeXOOup7IjDn2xy4WVFnE8gbwBlYZI5mFaX8sFawO+liieKPZJV9z/6GTOmQo" +
"M01z3KMP6XbGPWgix6o7L8ivs8H4gDzq15D5lf5RiLxGcjUCQQD7TdGn1yrPrmTW" +
"uu8wwRBHcpI+He2Ry1NjYmPLZj20hDfBhbgLoj7PNM7x3bfn1ULg5H2UFnygMvq4" +
"qMIGeoDLAkEAjwUQ9hYV+Uy1AsSf8pbJDHF7tcXFLQ1qlmoeOrt/RZmJhn0sgndD" +
"9k7o2OQj86aRKKLJIXFPtyiY8HlC1+gCOwJBAIh0rv0WJtbyeSroAm1UyAQjwCke" +
"kxtxbmwuxsVxVNwqVyQr+c3HYZedsyk+HVgzQsdfCplYxH8wb1fJuuFNr5UCQHsi" +
"iITnZQncIih8850gd36wIivRV78/Qtq4CMjWb3CUDZTuJqk5WBkzvUQnwFBhw66x" +
"4OtbLJ/sYyj/ri5HwcsCQQCaZiuXi6M3cZPtWDNuRch6q6sQDqDME8K0O8A7/Uto" +
"fUiF3Y57fqft3UZUROyjwmJmTdzx3ecdthaVYszU6iU2";
byte[] bPublicKey2 = Base64.getDecoder().decode(sPublicKey2.getBytes());
PublicKey publicKey2 = null;
byte[] bPrivateKey2 = Base64.getDecoder().decode(sPrivateKey2.getBytes());
PrivateKey privateKey2 = null;
try {
KeyFactory keyFactory2 = KeyFactory.getInstance("RSA");
X509EncodedKeySpec publicKeySpec
= new X509EncodedKeySpec(bPublicKey2);
publicKey2 = keyFactory2.generatePublic(publicKeySpec);
DerInputStream derReader = new DerInputStream(Base64.getDecoder().decode(sPrivateKey2));
DerValue[] seq = derReader.getSequence(0);
// skip version seq[0];
BigInteger modulus = seq[1].getBigInteger();
BigInteger publicExp = seq[2].getBigInteger();
BigInteger privateExp = seq[3].getBigInteger();
BigInteger prime1 = seq[4].getBigInteger();
BigInteger prime2 = seq[5].getBigInteger();
BigInteger exp1 = seq[6].getBigInteger();
BigInteger exp2 = seq[7].getBigInteger();
BigInteger crtCoef = seq[8].getBigInteger();
RSAPrivateCrtKeySpec keySpec =
new RSAPrivateCrtKeySpec(modulus, publicExp, privateExp, prime1, prime2, exp1, exp2, crtCoef);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
privateKey2 = keyFactory.generatePrivate(keySpec);
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
e.printStackTrace();
}
String sPlain1 = "Welcome to RSA";
String sPlain2 = null;
try {
Cipher cipher = Cipher.getInstance("RSA");
// 공개키 이용 암호화
cipher.init(Cipher.ENCRYPT_MODE, publicKey2);
byte[] bCipher1 = cipher.doFinal(sPlain1.getBytes());
String sCipherBase64 = Base64.getEncoder().encodeToString(bCipher1);
System.out.println(sCipherBase64);
// 개인키 이용 복호화
byte[] bCipher2 = Base64.getDecoder().decode(sCipherBase64.getBytes());
cipher.init(Cipher.DECRYPT_MODE, privateKey2);
byte[] bPlain2 = cipher.doFinal(bCipher2);
sPlain2 = new String(bPlain2);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
} catch (IllegalBlockSizeException e) {
e.printStackTrace();
} catch (BadPaddingException e) {
e.printStackTrace();
}
System.out.println("sPlain1 : " + sPlain1); // 평문(원본)
System.out.println("sPlain2 : " + sPlain2); // 평문(암호화후 복호화된 평문)
}
}
아래 부분이 핵심이라고 볼수 있습니다.
DerInputStream derReader = new DerInputStream(Base64.getDecoder().decode(sPrivateKey2));
DerValue[] seq = derReader.getSequence(0);
// skip version seq[0];
BigInteger modulus = seq[1].getBigInteger();
BigInteger publicExp = seq[2].getBigInteger();
BigInteger privateExp = seq[3].getBigInteger();
BigInteger prime1 = seq[4].getBigInteger();
BigInteger prime2 = seq[5].getBigInteger();
BigInteger exp1 = seq[6].getBigInteger();
BigInteger exp2 = seq[7].getBigInteger();
BigInteger crtCoef = seq[8].getBigInteger();
RSAPrivateCrtKeySpec keySpec =
new RSAPrivateCrtKeySpec(modulus, publicExp, privateExp, prime1, prime2, exp1, exp2, crtCoef);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
privateKey2 = keyFactory.generatePrivate(keySpec);
