AES加密IV [英] AES Encryption IV's
问题描述
我在下面使用这个（E.1）作为我的申请，显然有一个巨大的安全漏洞，我认识并理解。我对加密越来越感兴趣，并希望更好地理解它，我需要生成一个随机密钥和IV，但我不确定如何正确地做到这一点有人可以向我解释熟悉AES加密的人如何工作（IV& KEY）所以我以后能够更好地理解并且可以运用我的知识，本质上我只是想让代码更安全，谢谢。
I am using this below (E.1) for my application, there is obviously a huge glaring security hole in this that I recognize and understand. I have grown interested in encryption and want to understand it better, I need to generate a random key along with an IV but am unsure how to do so properly Can someone explain to me whom is familiar with AES encryption how this works (IV & KEY) So I am better able to understand in the future and can apply my knowledge, essentially I just want to make the code more secure, thank you.
（E.1）
byte[] key = "mykey".getBytes("UTF-8");
private byte[] getKeyBytes(final byte[] key) throws Exception {
byte[] keyBytes = new byte[16];
System.arraycopy(key, 0, keyBytes, 0, Math.min(key.length, keyBytes.length));
return keyBytes;
}
public Cipher getCipherEncrypt(final byte[] key) throws Exception {
byte[] keyBytes = getKeyBytes(key);
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");
IvParameterSpec ivParameterSpec = new IvParameterSpec(keyBytes);
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
return cipher;
}
public void encrypt(File in, File output, byte[] key) throws Exception {
Cipher cipher = getCipherEncrypt(key);
FileOutputStream fos = null;
CipherOutputStream cos = null;
FileInputStream fis = null;
try {
fis = new FileInputStream(in);
fos = new FileOutputStream(output);
cos = new CipherOutputStream(fos, cipher);
byte[] data = new byte[1024];
int read = fis.read(data);
while (read != -1) {
cos.write(data, 0, read);
read = fis.read(data);
System.out.println(new String(data, "UTF-8").trim());
}
cos.flush();
} finally {
System.out.println("performed encrypt method now closing streams:\n" + output.toString());
cos.close();
fos.close();
fis.close();
}
}
public void watchMeEncrypt(){
encrypt(file, new File ("example.txt),key);
推荐答案
AES密钥只包含随机字节。对于CBC模式，IV模式也应该是随机的（至少对攻击者而言）。所以通常你可以简单地使用 SecureRandom 实例来创建密钥和IV。然后IV可以包含在密文中;通常它只是放在它前面。
An AES key simply consists of random bytes. For CBC mode the IV mode should also be randomized (at least to an attacker). So in general you can simply use a SecureRandom instance to create the key and IV. The IV can then be included with the ciphertext; usually it is simply put in front of it.
使用Java最好使用 KeyGenerator 但是。如果你在SUN提供程序中查看它的实现，它可能会相同。但是使用 KeyGenerator 与各种密钥和提供商更兼容。很可能需要在智能卡和HSM中生成密钥。
With Java it is better to use a KeyGenerator though. If you look at the implementation of it in the SUN provider it will probably amount to the same thing. However using a KeyGenerator is more compatible with various kinds of keys and providers. It may well be that it is a requirement for generating keys in e.g. smart cards and HSM's.
所以让我们一起来用三种简单方法显示一个类：
So lets show a class with three simple methods:
package nl.owlstead.stackoverflow;
import static java.nio.charset.StandardCharsets.UTF_8;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.NoSuchAlgorithmException;
import java.security.Provider;
import java.security.SecureRandom;
import java.util.Optional;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
public class CreateKeyAndIVForAES_CBC {
public static SecretKey createKey(final String algorithm, final int keysize, final Optional<Provider> provider, final Optional<SecureRandom> rng) throws NoSuchAlgorithmException {
final KeyGenerator keyGenerator;
if (provider.isPresent()) {
keyGenerator = KeyGenerator.getInstance(algorithm, provider.get());
} else {
keyGenerator = KeyGenerator.getInstance(algorithm);
}
if (rng.isPresent()) {
keyGenerator.init(keysize, rng.get());
} else {
// not really needed for the Sun provider which handles null OK
keyGenerator.init(keysize);
}
return keyGenerator.generateKey();
}
public static IvParameterSpec createIV(final int ivSizeBytes, final Optional<SecureRandom> rng) {
final byte[] iv = new byte[ivSizeBytes];
final SecureRandom theRNG = rng.orElse(new SecureRandom());
theRNG.nextBytes(iv);
return new IvParameterSpec(iv);
}
public static IvParameterSpec readIV(final int ivSizeBytes, final InputStream is) throws IOException {
final byte[] iv = new byte[ivSizeBytes];
int offset = 0;
while (offset < ivSizeBytes) {
final int read = is.read(iv, offset, ivSizeBytes - offset);
if (read == -1) {
throw new IOException("Too few bytes for IV in input stream");
}
offset += read;
}
return new IvParameterSpec(iv);
}
public static void main(String[] args) throws Exception {
final SecureRandom rng = new SecureRandom();
// you somehow need to distribute this key
final SecretKey aesKey = createKey("AES", 128, Optional.empty(), Optional.of(rng));
final byte[] plaintext = "owlstead".getBytes(UTF_8);
final byte[] ciphertext;
{
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
final Cipher aesCBC = Cipher.getInstance("AES/CBC/PKCS5Padding");
final IvParameterSpec ivForCBC = createIV(aesCBC.getBlockSize(), Optional.of(rng));
aesCBC.init(Cipher.ENCRYPT_MODE, aesKey, ivForCBC);
baos.write(ivForCBC.getIV());
try (final CipherOutputStream cos = new CipherOutputStream(baos, aesCBC)) {
cos.write(plaintext);
}
ciphertext = baos.toByteArray();
}
final byte[] decrypted;
{
final ByteArrayInputStream bais = new ByteArrayInputStream(ciphertext);
final Cipher aesCBC = Cipher.getInstance("AES/CBC/PKCS5Padding");
final IvParameterSpec ivForCBC = readIV(aesCBC.getBlockSize(), bais);
aesCBC.init(Cipher.DECRYPT_MODE, aesKey, ivForCBC);
final byte[] buf = new byte[1_024];
try (final CipherInputStream cis = new CipherInputStream(bais, aesCBC);
final ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
int read;
while ((read = cis.read(buf)) != -1) {
baos.write(buf, 0, read);
}
decrypted = baos.toByteArray();
}
}
System.out.println(new String(decrypted, UTF_8));
}
}
请注意，您可能并不总是希望生成和分发AES密钥带外。以下是其他一些生成密钥的方法（第2部分）。您可能还想查看加密操作的更高级异常处理。
Note that you may not always want to generate and distribute an AES key "out-of-band". Here are a few other methods of generating a key (part #2 onwards). You may also want to take a look at more advanced exception handling for the cryptographic operation.
这篇关于AES加密IV的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
