Decrypt encypted data

EHR.network encrypts some critical secret data when shared with the apps. This is to improve security of the APIs. An example use case is the email & resetToken returned in the forgot password API.

This page explains how these can be decrypted in Java for further processing by the applications.

Requirements

1. Server public key - This can be obtained from the server admin

Java implementation

Java dependencies

import java.security.*;
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.security.spec.*;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import org.apache.commons.io.FileUtils;

Code snippet

publicKey = getKey(LoadConfig.getConfigValue("PUBLIC_KEY_PATH"));
String email = decrypt(objPass.getEmail());
String token = decrypt(objPass.getResetToken());

public static String decrypt(String data)
                  throws IllegalBlockSizeException, InvalidKeyException, BadPaddingException, NoSuchAlgorithmException,
                  NoSuchPaddingException, IOException, InvalidKeySpecException {
            return decrypt(data, getPublicKey(publicKey));
}

 public static String decrypt(String data, PublicKey publicKey) throws NoSuchPaddingException,
                  NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {

            String decryptedPassword = null;
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            cipher.init(Cipher.DECRYPT_MODE, publicKey);

            byte[] decryptedPasswordByte = cipher.doFinal(Base64.getDecoder().decode(data));
            decryptedPassword = new String(decryptedPasswordByte, StandardCharsets.UTF_8);
            return decryptedPassword;
  }

private static String getKey(String filename) throws IOException {
            // Read key from file
            String strKeyPEM = "";
            BufferedReader br = new BufferedReader(new FileReader(filename));
            String line;
            while ((line = br.readLine()) != null) {
                  strKeyPEM += line + "\n";
            }
            br.close();
            return strKeyPEM;
      }

public static PublicKey getPublicKey(String base4096PublicKey)
            throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {
        // String filename = LoadConfig.getConfigValue("PUBLIC_KEY_PATH");
        // String publicKeyPEM = FileUtils.readFileToString(new File(filename));

        String publicKeyPEM = base4096PublicKey;

        // strip of header, footer, newlines, whitespace
        publicKeyPEM = publicKeyPEM.replace("-----BEGIN PUBLIC KEY-----", "").replace("-----END PUBLIC KEY-----", "")
                .replaceAll("\\s", "");

        // decode to get the binary DER representation
        byte[] publicKeyDER = Base64.getDecoder().decode(publicKeyPEM);
        X509EncodedKeySpec keySpecX509 = new X509EncodedKeySpec(publicKeyDER);
        PublicKey pubKey = KeyFactory.getInstance("RSA").generatePublic(keySpecX509);
        return pubKey;
}

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Last update: 2022-12-02