问题描述
我已经编写了一个Java程序，要求用户指定一个随机密钥（以base 64编码），指定要加密的纯文本文件以及输出文件的名称（加密的文本文件）。 / p>
然后反向解密（密钥+输入的加密文件+输出的解密文件的名称）。
这与OpenSSL提供的行为非常相似。
我的Java代码使用模式AES/CBC/PKCS5PADDING。
我事先使用文件输出流将随机生成的初始化向量（16字节IV）附加到了密文中。然后，我相信密文输出流会在IV之后写入密文。
我可以确认通过加密和解密方法生成和获取的IV都是相同的（都可以使用base64编码打印出来，并且将匹配）。
但是，问题出在试图解密加密的文本。解密后的文本能够显示加密文本的后半部分（与原始纯文本的后半部分匹配）。
示例：
纯文本：my secret motto: i am awesome!
密文：<lots of encrypted characters>
解密后的文本：<a few encrypted characters> i am awesome!
上半部分似乎被覆盖，或者收集了一些奇怪的剩余加密文本。这使我相信我使用流对IV进行加密/解密的方式不太正确。
相关的执行代码是布尔值fileStoreIV为true时。 else代码用于用户同时提供密钥和IV作为输入。
因此，fout.write(initVector);和encryptedData.read(fileIV);是代码的主要位。
加密方法：
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,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,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,IOException,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,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,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,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");
其他说明：当我在纯文本文件之前和内部添加足够的空格时。我设法将足够多的文本移到上方，以显示解密的文件：<a few encrypted characters> my secret motto: i am awesome!。
解决方法
解密未成功运行的主要部分是您的Encrypt方法中的这段代码：
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,skeySpec,iv);
}
在fileStoreIV == true中，您没有为cipher.init函数指定IV。而且由于IV错误，解密后的明文的第一个块（AES为16个字节）被有效的随机垃圾所代替；根据其长度（根据@ dave_thompson_085的评论），它可能是纯文本的一半，全部或很小一部分。
我修改了您的代码，因为它由于其他一些错误而无法立即使用，但是我懒得去更正它们，而是在下面找到了完整的示例代码。
这是程序的输出，我的纯文本文件包含文本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,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,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,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,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,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,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,new IvParameterSpec(fileIV));
// ### leave out his line fileStoreIV = false;
}
int nread;
while ((nread = cipherInputStream.read(buffer)) > 0) {
out.write(buffer,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);
}
}