java.lang.IllegalArgumentException: bad base-64 when decrypting string

Question

I am trying to encrypt a string using the KeyStore and used this post as reference.

KeyPairGeneratorSpec replacement with KeyGenParameterSpec.Builder equivalents - Keystore operation failed

yet, I keep getting this "bad base-64" when I decrypt the string. I am not understanding exactly how to fix this. I understand that the encrypted string contains characters that the decryptor does not know. But I don't understand the fix.

I saw some posts like those, but did not help much since there is no code on the answers.

java.lang.IllegalArgumentException: bad base-64

This is a snipped of my the test code, can someone show me how I decrpyt my string?

Cipher inCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", "AndroidOpenSSL");
inCipher.init(Cipher.ENCRYPT_MODE, publicKey);

Cipher outCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", "AndroidOpenSSL");
outCipher.init(Cipher.DECRYPT_MODE, privateKey);

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
CipherOutputStream cipherOutputStream = new CipherOutputStream(
        outputStream, inCipher);
cipherOutputStream.write(plainText.getBytes("UTF-8"));
cipherOutputStream.close();

String ecryptedText = outputStream.toString();
Log.d(TAG, "Encrypt = " + ecryptedText);

String cipherText = ecryptedText;
CipherInputStream cipherInputStream = new CipherInputStream(
        new ByteArrayInputStream(Base64.decode(cipherText, Base64.DEFAULT)), outCipher);
ArrayList<Byte> values = new ArrayList<>();
int nextByte;
while ((nextByte = cipherInputStream.read()) != -1) {
    values.add((byte)nextByte);
}

byte[] bytes = new byte[values.size()];
for(int i = 0; i < bytes.length; i++) {
    bytes[i] = values.get(i).byteValue();
}

String finalText = new String(bytes, 0, bytes.length, "UTF-8");
Log.d(TAG, "Decrypt = " + ecryptedText);

50 pts of my reputation for grabs who can paste code that encrypts and decrypt ***in memory*** a string using the android keystore. I cannot use file access or shared preferences for the purpose of my app. I repeat it must be done in memory. The key is saved inside the KeyStore. — gmmo, Dec 09 '16 at 00:19
You set `cipherText` from `ecryptedText` and try to base64-decode it, but that **was not base64-encoded** in the first place. Use something like `ecryptedText = Base64.encode (/*BAOS*/ outputStream.toByteArray, Base64.DEFAULT);` — dave_thompson_085, Dec 09 '16 at 02:51
https://stackoverflow.com/questions/23241257/bad-base-64-error/23241611#23241611 this is the solution — user3727757, Sep 27 '18 at 03:44

Christos Lytras · Accepted Answer · 2016-12-12T09:06:39.063

Here is a working example on how you can use Android KeyStore to Encrypt/Decrypt memory strings by using ByteArrayOutputStream and ByteArrayInputStream. Notice the provider change, for >= 6 use "AndroidKeyStoreBCWorkaround" and for older versions use "AndroidOpenSSL". Also, you have to encode the encrypted data to Base64 string using Base64.encodeToString like this:

String ecryptedText = Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);

My final working example based on your code

try {
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(
            KeyProperties.KEY_ALGORITHM_RSA, "AndroidKeyStore");
    keyPairGenerator.initialize(
            new KeyGenParameterSpec.Builder(
                    "key1",
                    KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
                    .build());
    KeyPair keyPair = keyPairGenerator.generateKeyPair();

    // error in android 6: InvalidKeyException: Need RSA private or public key AndroidOpenSSL
    // error in android 5: NoSuchProviderException: Provider not available: AndroidKeyStoreBCWorkaround
    String provider = Build.VERSION.SDK_INT < Build.VERSION_CODES.M ? "AndroidOpenSSL" : "AndroidKeyStoreBCWorkaround";

    Cipher inCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", provider);
    inCipher.init(Cipher.ENCRYPT_MODE, keyPair.getPublic());

    Cipher outCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", provider);
    outCipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivate());

    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    CipherOutputStream cipherOutputStream = new CipherOutputStream(
            outputStream, inCipher);

    String plainText = "This is a text";

    cipherOutputStream.write(plainText.getBytes("UTF-8"));
    cipherOutputStream.close();

    String ecryptedText = Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);
    Log.d(TAG, "Encrypt = " + ecryptedText);

    String cipherText = ecryptedText;
    CipherInputStream cipherInputStream = new CipherInputStream(
            new ByteArrayInputStream(Base64.decode(cipherText, Base64.DEFAULT)), outCipher);

    ArrayList<Byte> values = new ArrayList<>();
    int nextByte;
    while ((nextByte = cipherInputStream.read()) != -1) {
        values.add((byte)nextByte);
    }

    byte[] bytes = new byte[values.size()];
    for(int i = 0; i < bytes.length; i++) {
        bytes[i] = values.get(i).byteValue();
    }

    String finalText = new String(bytes, 0, bytes.length, "UTF-8");
    Log.d(TAG, "Decrypt = " + finalText);
} catch (javax.crypto.NoSuchPaddingException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (IOException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (NoSuchAlgorithmException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (NoSuchProviderException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (InvalidAlgorithmParameterException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (InvalidKeyException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (UnsupportedOperationException e) {
    Log.e(TAG, Log.getStackTraceString(e));
}

OUTPUTS

D/MainActivity: Encrypt = rejkfeas3HgYnZOlC4S/R3KvlMTyiBjr5T6LqWGj9bq6nvpM0KBsoeYtr4OdCLITFX5GojuO4VpB
                Hy11n8zc9JcAx4IFW0Aw0/DfCmMDvIomQItBAaIWewZqNHc0UwS0y/JRhAe8SiTz5sFJ6Abvgax6
                vEfbYT0gzok+qtlfBNQLPvXejquhc0pZBaX1RgKDZyEJh3DBVRaFDgogK8XphaI/xtd1Cww9uO63
                QxA7HfrFUN8rJXrHF4EMi/yrDxs2xVHGF0v21xeuXRwLW9JXYn4fFAJJ0Jr8N5f03UDuKeNlI568
                RFVOGH7WpOLvKN4CDlsC+DT4Z8YVIOdtS/tO+Q==
D/MainActivity: Decrypt = This is a text

UPDATE

For Android API 19, you just have to use the previous KeyStore API KeyPairGeneratorSpec instead of KeyGenParameterSpec like this:

try {
    Calendar start = Calendar.getInstance();
    Calendar end = Calendar.getInstance();
    end.add(Calendar.YEAR, 1);

    KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(this)
        .setAlias("key1")
        .setSubject(new X500Principal("CN=Sample Name, O=Android Authority"))
        .setSerialNumber(BigInteger.ONE)
        .setStartDate(start.getTime())
        .setEndDate(end.getTime())
        .build();

    KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA", "AndroidKeyStore");
    generator.initialize(spec);

    // error in android 6: InvalidKeyException: Need RSA private or public key AndroidOpenSSL
    // error in android 5: NoSuchProviderException: Provider not available: AndroidKeyStoreBCWorkaround
    String provider = Build.VERSION.SDK_INT < Build.VERSION_CODES.M ? "AndroidOpenSSL" : "AndroidKeyStoreBCWorkaround";

    KeyPair keyPair = generator.generateKeyPair();

    Cipher inCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", provider);
    inCipher.init(Cipher.ENCRYPT_MODE, keyPair.getPublic());

    Cipher outCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", provider);
    outCipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivate());


    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    CipherOutputStream cipherOutputStream = new CipherOutputStream(
            outputStream, inCipher);

    String plainText = "This is a text";

    cipherOutputStream.write(plainText.getBytes("UTF-8"));
    cipherOutputStream.close();

    String ecryptedText = Base64.encodeToString(outputStream.toByteArray(), Base64.DEFAULT);
    Log.d(TAG, "Encrypt = " + ecryptedText);

    String cipherText = ecryptedText;
    CipherInputStream cipherInputStream = new CipherInputStream(
            new ByteArrayInputStream(Base64.decode(cipherText, Base64.DEFAULT)), outCipher);

    ArrayList<Byte> values = new ArrayList<>();
    int nextByte;
    while ((nextByte = cipherInputStream.read()) != -1) {
        values.add((byte)nextByte);
    }

    byte[] bytes = new byte[values.size()];
    for(int i = 0; i < bytes.length; i++) {
        bytes[i] = values.get(i).byteValue();
    }

    String finalText = new String(bytes, 0, bytes.length, "UTF-8");
    Log.d(TAG, "Decrypt = " + finalText);
} catch (javax.crypto.NoSuchPaddingException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (IOException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (NoSuchAlgorithmException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (NoSuchProviderException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (InvalidAlgorithmParameterException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (InvalidKeyException e) {
    Log.e(TAG, Log.getStackTraceString(e));
} catch (UnsupportedOperationException e) {
    Log.e(TAG, Log.getStackTraceString(e));
}

Christos, thanks for the code. One thing I forgot to mentioned is that it needs to work on API 19. The code above only works on API 23 and above. I need to support old devices. Would you happen to know how to make it work on API level 19? — gmmo, Dec 12 '16 at 02:08
@gmmo It's really easy, you just have to use the old KeyStore Spec API. Please have a look at my updated answer. — Christos Lytras, Dec 12 '16 at 08:59

java.lang.IllegalArgumentException: bad base-64 when decrypting string

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