JavaによるRSAの実装

RSAUtl.java

import java.util.Base64;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.PrivateKey;
import java.security.spec.X509EncodedKeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import javax.crypto.Cipher;
import javax.crypto.spec.OAEPParameterSpec;
import java.security.spec.MGF1ParameterSpec;
import javax.crypto.spec.PSource;

/*
 * Utility Class for Encrypt/Decrypt with RSA
 *
 * How to load Java into schema APEXDEV
 * loadjava -force -verbose -resolve -u apexdev/****@localhost/xepdb1 RSAUtl.java
 *
 * Wrapper Function:
--
create or replace function rsautl_encrypt
(
    text varchar2,
    key  varchar2
    alg varchar2    // Valid only SHA-256
) return varchar2
as
language java name 'RSAUtl.encrypt(java.lang.String, java.lang.String, java.lang.String) return java.lang.String';
/

create or replace function rsautl_decrypt
(
    text varchar2,
    key  varchar2,
    alg varchar2  // Valid only SHA-256
) return varchar2
as
language java name 'RSAUtl.decrypt(java.lang.String, java.lang.String, java.lang.String) return java.lang.String';
/
--
 */
public class RSAUtl {
  /*
   * Encryption
   */
  public static String encrypt(String text, String key, String alg)
  throws Exception
  {
    MGF1ParameterSpec mgf  = new MGF1ParameterSpec(alg);
    OAEPParameterSpec spec = new OAEPParameterSpec(alg,"MGF1",mgf,PSource.PSpecified.DEFAULT);
    byte[] data   = text.getBytes("UTF-8");          // plain text into bytes
    byte[] pkdata = Base64.getDecoder().decode(key); // PEM text key into DER
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PublicKey  publicKey  = keyFactory.generatePublic(new X509EncodedKeySpec(pkdata));
    Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPPadding");
    cipher.init(Cipher.ENCRYPT_MODE, publicKey, spec);
    return Base64.getEncoder().encodeToString(cipher.doFinal(data));
  }
  /*
   * Decryption - PKCS#8
   */
  public static String decrypt(String text, String key, String alg)
  throws Exception
  {
    MGF1ParameterSpec mgf  = new MGF1ParameterSpec(alg);
    OAEPParameterSpec spec = new OAEPParameterSpec(alg,"MGF1",mgf,PSource.PSpecified.DEFAULT);
    byte[] data   = Base64.getDecoder().decode(text); // base64 cipher text into bytes
    byte[] pkdata = Base64.getDecoder().decode(key);  // PEM text key into DER
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PrivateKey privateKey = keyFactory.generatePrivate(new PKCS8EncodedKeySpec(pkdata));
    Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPPadding");
    cipher.init(Cipher.DECRYPT_MODE, privateKey, spec);
    return new String(cipher.doFinal(data),"UTF-8");
  }
}