使用附加的初始化向量 java 使用流加密和解密文件

Question

我编写了一个 Java 程序，它要求用户指定一个随机密钥（以 base 64 编码），指定要加密的明文文件，以及输出文件的名称（加密的文本文件。)

然后逆向解密（秘钥+输入加密文件+输出解密文件名）

这与 OpenSSL 提供的行为非常相似。

我的 java 代码使用模式 AES/CBC/PKCS5PADDING.

我预先使用文件输出流将随机生成的初始化向量（16 字节 IV）附加到我的密文中。然后我相信密码输出流在IV之后写入密文。

我可以确认从加密和解密方法生成和获取的 IV 是相同的（都可以用 base64 编码打印出来，并且会匹配）。

但是，问题在于尝试解密加密文本。解密后的文本能够显示加密文本的后半部分（与原始明文的后半部分匹配）。

示例：

纯文本：my secret motto: i am awesome!

密文：<lots of encrypted characters>

解密文本：<a few encrypted characters> i am awesome!

虽然前半部分似乎被覆盖了，或者可能收集了一些奇怪的剩余加密文本。这让我相信我 encrypting/decrypting IV 使用流的方式有些不对劲。

相关执行的代码是布尔值fileStoreIV为真时。 else 代码用于用户同时提供密钥和 IV 作为输入的情况。

因此fout.write(initVector);和encryptedData.read(fileIV);是代码的主要部分。

加密方式：

private static void encrypt(byte[] key, byte[] initVector, String inputFile, String outputFile) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, IOException {
    //Initalisation for encryption
    Cipher cipher = Cipher.getInstance(CIPHER);
    if(fileStoreIV) {
        SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    }
    else {
        IvParameterSpec iv = new IvParameterSpec(initVector);
        SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
    }
    
    //File error checking
    File loadFile = new File(inputFile);
    Path saveFile = Paths.get(outputFile);
    
    Path loadFilePath = Paths.get(inputFile);
    if (!Files.exists(loadFilePath)){
        System.out.println("The inputFile you specified does not exist");
        return;
    }
    
    Path parentDir = saveFile.getParent();
    if (parentDir != null && !Files.exists(parentDir)) {
        System.out.println("The outputFile directory/s you specified does not exist");
        return;
    }
    
    System.out.println("Secret key is " + Base64.getEncoder().encodeToString(key));
    System.out.println("IV is " + Base64.getEncoder().encodeToString(initVector));

    //Special file reading and writing with 'Cipher Stream'
    try (InputStream fin = FileEncryptor.class.getResourceAsStream(loadFile.getName());
            OutputStream fout = Files.newOutputStream(saveFile);
            
            CipherOutputStream cipherOut = new CipherOutputStream(fout, cipher) {
    }) {
        final byte[] bytes = new byte[1024];
        for(int length=fin.read(bytes); length!=-1; length = fin.read(bytes)){
            
            
            if(fileStoreIV) {
                fout.write(initVector);
                fileStoreIV = false;
            }
            
            cipherOut.write(bytes, 0, length);
            
        }
    } catch (IOException e) {
        System.out.println("Something went wrong with reading and writing these files!");
        System.out.println("Please check you have the latest version of this program");
        System.out.println("Contact your IT admin to make sure you have sufficient privileges");
    }
    System.out.println("SUCCESS! Encryption finished, saved at specified location");

解密方法：

private static void decrypt(String inputKEY, String inputIV, String inputFile, String outputFile) throws NoSuchAlgorithmException, NoSuchPaddingException, IOException, InvalidKeyException, InvalidAlgorithmParameterException {
    //Initalisation for decryption
    Cipher cipher = Cipher.getInstance(CIPHER);
    if(!fileStoreIV) {
        IvParameterSpec iv = new IvParameterSpec(Base64.getDecoder().decode(inputIV));
        SecretKeySpec skeySpec = new SecretKeySpec(Base64.getDecoder().decode(inputKEY), ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
    }
    
    Path saveFile = Paths.get(outputFile);
    
    Path loadFilePath = Paths.get(inputFile);
    if (!Files.exists(loadFilePath)){
        System.out.println("The inputFile you specified does not exist");
        return;
    }
    
    Path parentDir = saveFile.getParent();
    if (parentDir != null && !Files.exists(parentDir)) {
        System.out.println("The outputFile directory/s you specified does not exist");
        return;
    }
    
    InputStream encryptedData = Files.newInputStream(loadFilePath);
    
    if(fileStoreIV) {
        {
            byte[] fileIV = new byte[16];
            encryptedData.read(fileIV);
            System.out.println(Base64.getEncoder().encodeToString(fileIV));
                SecretKeySpec skeySpec = new SecretKeySpec(Base64.getDecoder().decode(inputKEY), ALGORITHM);
                cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(fileIV));
                fileStoreIV = false;
        }
    }
    
        try (CipherInputStream decryptStream = new CipherInputStream(encryptedData, cipher);    
        OutputStream decryptedOut = Files.newOutputStream(saveFile)){
        final byte[] bytes = new byte[1024];
        for(int length=decryptStream.read(bytes); length!=-1; length = decryptStream.read(bytes)){
            decryptedOut.write(bytes, 0, length);
        }
    } catch (IOException e) {
        System.out.println("Something went wrong with reading and writing these files!");
        System.out.println("Please check you have the latest version of this program");
        System.out.println("Contact your IT admin to make sure you have sufficient privileges");
    }
    
    System.out.println("SUCESS! Decryption finished, saved at specified location");

附加说明：当我在纯文本文件之前和内部添加足够的空格时。我设法移动了足够多的文本，以显示解密文件：<a few encrypted characters> my secret motto: i am awesome!.

Answer 1

解密未成功运行的主要部分是 Encrypt-method 中的这部分代码：

if(fileStoreIV) {
     SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
     cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
} else {
     IvParameterSpec iv = new IvParameterSpec(initVector);
     SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
     cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
}

当 fileStoreIV == true 没有为 cipher.init 函数指定 IV 时。并且由于 IV 错误，解密明文的第一个块（AES 为 16 个字节）被有效地随机垃圾替换；这可能是明文的一半、全部或一小部分，具体取决于其长度（根据 @dave_thompson_085 的评论）。

我修改了你的代码，因为它由于一些其他错误而没有运行开箱即用，但我懒得更正它们，而是你找到了完整的运行ning 示例代码下面。

这是程序的输出，我的 plaintext-file 包含文本 The quick brown fox jumps over the lazy dog:

Secret key is S2guVMqVk8goYy3QsgBSMmjLLCyvoknprTGoFsxMZEo=
IV is VFIYWeCT6ixg/lwk9bBQ9g==
SUCCESS! Encryption finished, saved at specified location
SUCESS! Decryption finished, saved at specified location
Content of file decryptedtext.txt
The quick brown fox jumps over the lazy dog

代码：

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;

public class FileEncryptorSo {
    static String ALGORITHM = "AES";
    static String CIPHER = "AES/CBC/PKCS5PADDING";
    static boolean fileStoreIV = true;

    public static void main(String[] args) throws IOException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException {
        System.out.println("");
        String plaintextFilename = "plaintext.txt";
        String ciphertextFilename = "ciphertext.enc";
        String decryptedFilename = "decryptedtext.txt";
        // random aes 256 key
        byte[] key = new byte[32];
        SecureRandom secureRandom = new SecureRandom();
        secureRandom.nextBytes(key);
        // random iv
        byte[] iv = new byte[16];
        secureRandom.nextBytes(iv);
        encrypt(key, iv, plaintextFilename, ciphertextFilename);
        decrypt(Base64.getEncoder().encodeToString(key), Base64.getEncoder().encodeToString(iv), ciphertextFilename, decryptedFilename);
        printTextfile(decryptedFilename);
    }

    private static void encrypt(byte[] key, byte[] initVector, String inputFile, String outputFile)
            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException {
        //Initalisation for encryption
        Cipher cipher = Cipher.getInstance(CIPHER);
        IvParameterSpec iv = new IvParameterSpec(initVector);
        SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
        /* ### leave out this part !
        if (fileStoreIV) {
            SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        } else {
            IvParameterSpec iv = new IvParameterSpec(initVector);
            SecretKeySpec skeySpec = new SecretKeySpec(key, ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
        }
         */
        //File error checking
        // ### not used File loadFile = new File(inputFile);
        Path saveFile = Paths.get(outputFile);
        Path loadFilePath = Paths.get(inputFile);
        if (!Files.exists(loadFilePath)) {
            System.out.println("The inputFile you specified does not exist");
            return;
        }
        Path parentDir = saveFile.getParent();
        if (parentDir != null && !Files.exists(parentDir)) {
            System.out.println("The outputFile directory/s you specified does not exist");
            return;
        }
        System.out.println("Secret key is " + Base64.getEncoder().encodeToString(key));
        System.out.println("IV is " + Base64.getEncoder().encodeToString(initVector));
        try (FileInputStream in = new FileInputStream(inputFile);
             FileOutputStream out = new FileOutputStream(outputFile);
             CipherOutputStream encryptedOutputStream = new CipherOutputStream(out, cipher);) {
            if (fileStoreIV) {
                out.write(initVector);
                // ### leave out this line fileStoreIV = false;
            }
            byte[] buffer = new byte[1024];
            int nread;
            while ((nread = in.read(buffer)) > 0) {
                encryptedOutputStream.write(buffer, 0, nread);
            }
            encryptedOutputStream.flush();
        } catch (IOException e) {
            System.out.println("Something went wrong with reading and writing these files!");
            System.out.println("Please check you have the latest version of this program");
            System.out.println("Contact your IT admin to make sure you have sufficient privileges");
        }
        System.out.println("SUCCESS! Encryption finished, saved at specified location");
    }

    private static void decrypt(String inputKEY, String inputIV, String inputFile, String outputFile)
            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException {
        //Initalisation for decryption
        Cipher cipher = Cipher.getInstance(CIPHER);
        if (!fileStoreIV) {
            IvParameterSpec iv = new IvParameterSpec(Base64.getDecoder().decode(inputIV));
            SecretKeySpec skeySpec = new SecretKeySpec(Base64.getDecoder().decode(inputKEY), ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
        }
        Path saveFile = Paths.get(outputFile);
        Path loadFilePath = Paths.get(inputFile);
        if (!Files.exists(loadFilePath)) {
            System.out.println("The inputFile you specified does not exist");
            return;
        }
        Path parentDir = saveFile.getParent();
        if (parentDir != null && !Files.exists(parentDir)) {
            System.out.println("The outputFile directory/s you specified does not exist");
            return;
        }
        //byte[] fileIV = new byte[16];
        try (FileInputStream in = new FileInputStream(inputFile);
             CipherInputStream cipherInputStream = new CipherInputStream(in, cipher);
             FileOutputStream out = new FileOutputStream(outputFile))
        {
            byte[] buffer = new byte[1024];
            if (fileStoreIV) {
                byte[] fileIV = new byte[16];
                in.read(fileIV);
                SecretKeySpec skeySpec = new SecretKeySpec(Base64.getDecoder().decode(inputKEY), ALGORITHM);
                cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(fileIV));
                // ### leave out his line fileStoreIV = false;
            }
            int nread;
            while ((nread = cipherInputStream.read(buffer)) > 0) {
                out.write(buffer, 0, nread);
            }
            out.flush();
        } catch (IOException e) {
            System.out.println("Something went wrong with reading and writing these files!");
            System.out.println("Please check you have the latest version of this program");
            System.out.println("Contact your IT admin to make sure you have sufficient privileges");
        }
        System.out.println("SUCESS! Decryption finished, saved at specified location");
    }

    private static void printTextfile (String filename) throws IOException {
        File file = new File(filename);
        FileInputStream fis = new FileInputStream(file);
        byte[] data = new byte[(int) file.length()];
        fis.read(data);
        fis.close();
        String str = new String(data, "UTF-8");
        System.out.println("Content of file " + filename + "\n" + str);
    }
}

使用附加的初始化向量 java 使用流加密和解密文件

Encrypt and decrypt a file with streams, using an appended initalisation vector java

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