Cannot decrypt when encrypted using AES/ECB/PKCS5Padding - input length must be multiple of 16

Question

I have this encryption code which works no problem. I can decrypt the text it encrypts in another language, but I need to decrypt it in java now.

 private static final String AES = "AES";
    private static final String CBC_BLOCK = "CBC";
    private static final String ECB_BLOCK = "ECB";
    private static final String PADDING = "PKCS5Padding";
    private static final String AES_CBC_PCKS5_CIPHER_CONFIG = AES + "/" + CBC_BLOCK + "/" + PADDING;
    private static final String AES_ECB_PCKS5_CIPHER_CONFIG = AES + "/" + ECB_BLOCK + "/" + PADDING;

 public static String encryptInAesEcbPkcs5Padding(String salt, String message) {
        String encryptedMessage = "";
        SecretKeySpec key = null;
        try {
            if (message != null && !message.equals("")) {
                key = new SecretKeySpec(salt.getBytes(StandardCharsets.UTF_8), AES);
                Cipher cipher = Cipher.getInstance(AES_ECB_PCKS5_CIPHER_CONFIG);
                cipher.init(Cipher.ENCRYPT_MODE, key);
                encryptedMessage = convertMessageToBase64(cipher.doFinal(message.getBytes(StandardCharsets.UTF_8)));
            }
        } catch (NoSuchAlgorithmException e) {
            LOGGER.error(LogPreFix.ERROR + "No such algorithm [" + AES + "]", e);
        } catch (NoSuchPaddingException e) {
            LOGGER.error(LogPreFix.ERROR + "No such padding for algorithm [" + AES + "]", e);
        } catch (IllegalBlockSizeException e) {
            LOGGER.error(LogPreFix.ERROR + "Invalid block size for [" + AES + "/" + ECB_BLOCK + "]", e);
        } catch (BadPaddingException e) {
            LOGGER.error(LogPreFix.ERROR + "Invalid padding [" + PADDING + "]", e);
        } catch (InvalidKeyException e) {
            LOGGER.error("Invalid key [" + key + "]", e);
        }
        return encryptedMessage;
    }

Trying to decrypt with this code. I am using the exact same salt as the encryption and passing in the string the encrypter creates as the "message"

public static String decrypt(String message, String salt) throws InvalidAlgorithmParameterException {
        SecretKeySpec key = null;
        String string = null;
        try {
            if (message != null && !message.equals("")) {
                key = new SecretKeySpec(salt.getBytes(StandardCharsets.UTF_8), AES);
                Cipher cipher = Cipher.getInstance(AES_ECB_PCKS5_CIPHER_CONFIG);
                cipher.init(Cipher.DECRYPT_MODE, key);
                byte[] decrypted = cipher.doFinal(message.getBytes(StandardCharsets.UTF_8));
                string = new String(decrypted);
            }
        } catch (NoSuchAlgorithmException e) {
            LOGGER.error(LogPreFix.ERROR + "No such algorithm [" + AES + "]", e);
        } catch (NoSuchPaddingException e) {
            LOGGER.error(LogPreFix.ERROR + "No such padding for algorithm [" + AES + "]", e);
        } catch (IllegalBlockSizeException e) {
            LOGGER.error(LogPreFix.ERROR + "Invalid block size for [" + AES + "/" + ECB_BLOCK + "]", e);
        } catch (BadPaddingException e) {
            LOGGER.error(LogPreFix.ERROR + "Invalid padding [" + PADDING + "]", e);
        } catch (InvalidKeyException e) {
            LOGGER.error("Invalid key [" + key + "]", e);
        }
        return string;
    }

But i get this error, what am i doing wrong? Seems like it should work. I tried padding the encrypted text with "=" added until it is divisible by 16 but that returns a bad padding error.

javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:750)
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:676)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:313)
    at javax.crypto.Cipher.doFinal(Cipher.java:2087)

This could be of help: http://stackoverflow.com/a/5760584/1416629 — pratnala, Aug 03 '16 at 17:57
Trying this, makes complete sense, just not getting the decoding quite right yet. Will update once i fix it. — wondergoat77, Aug 03 '16 at 19:11
tried doing this: byte[] bytes = Base64.decodeBase64(message); String decoded = new String(bytes); but this is not working for me, the output is symbols/gibberish — wondergoat77, Aug 03 '16 at 19:15
First, as soon as you encode to base64, decode it back at that point. Print encrypted version, encoded version and the decoded version. All in your encrypted code. — pratnala, Aug 03 '16 at 19:23
I dont really have that option right now, the encrypted code was run months ago on some strings, I need to now decode them in java. — wondergoat77, Aug 03 '16 at 19:26
@pratnala got it decoded, now trying to decrypt i get javax.crypto.BadPaddingException: Given final block not properly padded — wondergoat77, Aug 03 '16 at 20:01
When i try to remove padding by either change the cipher instance to just AES or AES/ECB/NoPadding, i get it decrypted but its gibberish/symbols — wondergoat77, Aug 03 '16 at 20:10
Since this is really a different problem, I posted a different question. Go ahead an add your answer if you want and i will mark it correct. The decoding got me past the error in this post. — wondergoat77, Aug 03 '16 at 20:15
Added as answer. Would help others if they have similar errors :) — pratnala, Aug 04 '16 at 20:07

score 1 · Accepted Answer · answered Aug 04 '16 at 20:07

1

Do Base64 decoding first to reverse the Base64 encoding performed in the original encryption process.

answered Aug 04 '16 at 20:07

pratnala

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Cannot decrypt when encrypted using AES/ECB/PKCS5Padding - input length must be multiple of 16

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