java 尝试使用 AES 加密和解密字符串时出现 IllegalBlockSizeException

IllegalBlockSizeException when trying to encrypt and decrypt a string with AES

提问by Oleksiy

I have a hardcoded key with which I want to encrypt a string before storing it in SharedPreferences. This is the code I have so far:

我有一个硬编码的密钥，我想用它在将字符串存储在SharedPreferences. 这是我到目前为止的代码：

public class TokenEncryptor {

    private final static String TOKEN_KEY = "91a29fa7w46d8x41";

    public static String encrypt(String plain) {
        try {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            AlgorithmParameterSpec ivSpec = new IvParameterSpec(new byte[16]);
            SecretKeySpec newKey = new SecretKeySpec(TOKEN_KEY.getBytes(), "AES");
            cipher.init(Cipher.ENCRYPT_MODE, newKey, ivSpec);
            return new String(cipher.doFinal(plain.getBytes()));
        } catch (Exception e) {
            Ln.e(e);
            return null;
        }
    }

    public static String decrypt(String encoded) {
        try {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            AlgorithmParameterSpec ivSpec = new IvParameterSpec(new byte[16]);
            SecretKeySpec newKey = new SecretKeySpec(TOKEN_KEY.getBytes(), "AES");
            cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec);
            return new String(cipher.doFinal(encoded.getBytes()));
        } catch (Exception e) {
            Ln.e(e);
            return null;
        }
    }
}

It seems to be catching an exception at the end of decryptmethod:

它似乎在decrypt方法结束时捕获异常：

javax.crypto.IllegalBlockSizeException: error:0606506D:digital envelope routines:EVP_DecryptFinal_ex:wrong final block length

javax.crypto.IllegalBlockSizeException: error:0606506D:digital envelope routines:EVP_DecryptFinal_ex:wrong final block length

Can someone point me in the right direction? I have a feeling I'm doing something wrong instantiating IvParameterSpec.

有人可以指出我正确的方向吗？我有一种感觉，我正在做一些错误的实例化IvParameterSpec。

回答by rossum

When you encrypt a string with AES, you get an array of bytes back. Trying to convert those bytes directly to a string (new String(cipher.doFinal(plaintextBytes))) will cause all sorts of problems. If you require the output from your encryption method to be a string, then use Base64rather than attempting a direct conversion. In your decryption method, convert the Base64string back into a byte array before decrypting the byte array.

当你用 AES 加密一个字符串时，你会得到一个字节数组。尝试将这些字节直接转换为字符串 ( new String(cipher.doFinal(plaintextBytes))) 会导致各种问题。如果您要求加密方法的输出是字符串，请使用Base64而不是尝试直接转换。在您的解密方法中，Base64在解密字节数组之前，将字符串转换回字节数组。

Also, do not use getBytes()since the output depends on the system defaults. Use getBytes("utf-8")or whatever. That eliminates ambiguity.

另外，不要使用，getBytes()因为输出取决于系统默认值。使用getBytes("utf-8")什么的。这消除了歧义。

回答by Oleksiy

Just in case anyone is interested (or feels too lazy to do their research), here is the the result code for AES-256encryption and decryption that I put together, with help from the accepted answer and comments:

以防万一有人感兴趣（或觉得懒得做研究），这里是AES-256我放在一起的加密和解密结果代码，在已接受的答案和评论的帮助下：

public class TokenEncryptor {

    private final static String TOKEN_KEY = "fqJfdzGDvfwbedsKSUGty3VZ9taXxMVw";

    public static String encrypt(String plain) {
        try {
            byte[] iv = new byte[16];
            new SecureRandom().nextBytes(iv);
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(TOKEN_KEY.getBytes("utf-8"), "AES"), new IvParameterSpec(iv));
            byte[] cipherText = cipher.doFinal(plain.getBytes("utf-8"));
            byte[] ivAndCipherText = getCombinedArray(iv, cipherText);
            return Base64.encodeToString(ivAndCipherText, Base64.NO_WRAP);
        } catch (Exception e) {
            Ln.e(e);
            return null;
        }
    }

    public static String decrypt(String encoded) {
        try {
            byte[] ivAndCipherText = Base64.decode(encoded, Base64.NO_WRAP);
            byte[] iv = Arrays.copyOfRange(ivAndCipherText, 0, 16);
            byte[] cipherText = Arrays.copyOfRange(ivAndCipherText, 16, ivAndCipherText.length);

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(TOKEN_KEY.getBytes("utf-8"), "AES"), new IvParameterSpec(iv));
            return new String(cipher.doFinal(cipherText), "utf-8");
        } catch (Exception e) {
            Ln.e(e);
            return null;
        }
    }

    private static byte[] getCombinedArray(byte[] one, byte[] two) {
        byte[] combined = new byte[one.length + two.length];
        for (int i = 0; i < combined.length; ++i) {
            combined[i] = i < one.length ? one[i] : two[i - one.length];
        }
        return combined;
    }

}

回答by Sam Reyes

It's an extension of Artjom B answer and working for me.

这是 Artjom B answer 的扩展，对我来说有效。

public String encryptMsg(String message, SecretKey secret)
            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidParameterSpecException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException {
        Cipher cipher = null;
        cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secret);
        byte[] cipherText = cipher.doFinal(message.getBytes("UTF-8"));
        return Base64.encodeToString(cipherText, Base64.NO_WRAP);
    }

public String decryptMsg(String cipherText, SecretKey secret)
        throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidParameterSpecException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException {
    Cipher cipher = null;
    cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    cipher.init(Cipher.DECRYPT_MODE, secret);
    byte[] decode = Base64.decode(cipherText, Base64.NO_WRAP);
    String decryptString = new String(cipher.doFinal(decode), "UTF-8");
    return decryptString;
}

回答by Kasim Rangwala

Kotlin version of @Oleksiy 's answer.

@Oleksiy 答案的 Kotlin 版本。

<script src="https://gist.github.com/kasim1011/a5a9644a60c33a4df3c29f4b34cf93a4.js"></script>

import android.util.Base64
import java.util.*
import javax.crypto.Cipher
import javax.crypto.spec.IvParameterSpec
import javax.crypto.spec.SecretKeySpec

private const val algorithm = "AES"
private const val tokenKey = "fqJfdzGDvfwbedsKSUGty3VZ9taXxMVw"
private const val padding = "AES/CBC/PKCS5Padding"
private const val ivSize = 16

fun String.encryptAES(): String {
    val tokenBytes = tokenKey.toByteArray(Charsets.UTF_8)
    val secretKey = SecretKeySpec(tokenBytes, algorithm)

    val ivByteArray = ByteArray(ivSize)
    val iv = IvParameterSpec(ivByteArray)

    val cipher = Cipher.getInstance(padding)
    cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv)

    val cipherText = cipher.doFinal(toByteArray(Charsets.UTF_8))
    val ivAndCipherText = getCombinedArray(ivByteArray, cipherText)

    return Base64.encodeToString(ivAndCipherText, Base64.NO_WRAP)
}

fun String.decryptAES(): String {
    val tokenBytes = tokenKey.toByteArray(Charsets.UTF_8)
    val secretKey = SecretKeySpec(tokenBytes, algorithm)

    val ivAndCipherText = Base64.decode(this, Base64.NO_WRAP)
    val cipherText = Arrays.copyOfRange(ivAndCipherText, ivSize, ivAndCipherText.size)

    val ivByteArray = Arrays.copyOfRange(ivAndCipherText, 0, ivSize)
    val iv = IvParameterSpec(ivByteArray)

    val cipher = Cipher.getInstance(padding)
    cipher.init(Cipher.DECRYPT_MODE, secretKey, iv)

    return cipher.doFinal(cipherText).toString(Charsets.UTF_8)
}

private fun getCombinedArray(one: ByteArray, two: ByteArray): ByteArray {
    val combined = ByteArray(one.size + two.size)
    for (i in combined.indices) {
        combined[i] = if (i < one.size) one[i] else two[i - one.size]
    }
    return combined
}