Everbook Decryptor

Main.java

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.UUID;
import java.util.stream.Collectors;
import java.util.zip.GZIPInputStream;

public class Main {
    static String get(byte[] bytes) {
        StringBuilder out = new StringBuilder();
        for (byte b : bytes) out.append(String.format("%02X", b));
        return out.toString();
    }

    public static void main(String[] args) throws Throwable {
        if (args.length < 1) {
            System.out.println("java -cp . Main [everbook file name]");
            return;
        }
        File book = new File(args[0]);
        String uuid = Arrays.stream(book.getName().split("-")).skip(1).collect(Collectors.joining("-")).substring(0, 36);

        UUID uid = UUID.fromString(uuid);
        System.out.println("Your UUID: " + uid);

        ByteBuffer buffer = ByteBuffer.allocate(16);
        buffer.putLong(uid.getMostSignificantBits());
        buffer.putLong(uid.getLeastSignificantBits());
        System.out.println("Your key:  " + get(buffer.array()));

        DataInputStream ins = new DataInputStream(new FileInputStream(book));
        byte[] iv = new byte[16];
        ins.read(iv);
        byte[] rest = ins.readAllBytes();
        System.out.println("Your IV:   " + get(iv));


        SecretKeySpec spec = new SecretKeySpec(buffer.array(), "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

        cipher.init(Cipher.DECRYPT_MODE, spec, new IvParameterSpec(iv));
        byte[] output = cipher.doFinal(rest);

        if (args.length != 2) {
            output = new GZIPInputStream(new ByteArrayInputStream(output)).readAllBytes(); // for comfort
            if (!(output[0] == 0x0A && output[1] == 0x00 && output[2] == 0x00))
                System.err.println("Decryption may have failed, no unnamed root compound tag.");
        }

        FileOutputStream stream = new FileOutputStream("decrypted.dat");
        stream.write(output);
        stream.flush();
    }
}

usage.md

How to use

javac Main.java
java -cp . Main [EVERBOOK FILE NAME] [extra arg if you want it compressed]

Referenced works

Talia12/Hexal (Everbook.kt)
Talia12/Hexal (FileEncryptorDecryptor.kt)