When i use this code on android Marshmallow(Android 6.0.1) ,the decryption is Ok but when i run on device with android Oreo(Android 8) the decryption value is not the same and data is not Correct.
private void decrypt(Cipher cipher, Uri uri) throws Exception {
long a = 113845229;
InputStream inputStream = getContentResolver().openInputStream(uri);
CipherInputStream cipherInputStream = new CipherInputStream(inputStream, cipher);
cipherInputStream.skip(a);
byte[] buffer = new byte[8];
cipherInputStream.read(buffer);
}
// create cipher
private Cipher createCipher(byte[] iv, byte[] salt, String password) throws Exception {
IvParameterSpec mIvParameterSpec = new IvParameterSpec(iv);
SecretKeySpec mSecretKeySpec = generate(password, salt);
Cipher mCipher = Cipher.getInstance("AES/CTR/NoPadding");
mCipher.init(Cipher.DECRYPT_MODE, mSecretKeySpec, mIvParameterSpec);
return mCipher;
}
// generate key
private SecretKeySpec generate(String password, byte[] salt) throws Exception {
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(salt);
byte[] key = md.digest(password.getBytes(StandardCharsets.UTF_8));
return new SecretKeySpec(key, "AES");
}
buffer data is ok in android 6 but in android 8 the data is not correct.
I came to the conclusion after research .you should implement InputStream with specific Cipher.
private static final int AES_BLOCK_SIZE = 16;
private InputStream mUpstream;
private Cipher mCipher;
private SecretKeySpec mSecretKeySpec;
private IvParameterSpec mIvParameterSpec;
public StreamingCipherInputStream(InputStream inputStream, Cipher cipher,
SecretKeySpec secretKeySpec, IvParameterSpec ivParameterSpec) {
super(inputStream, cipher);
mUpstream = inputStream;
mCipher = cipher;
mSecretKeySpec = secretKeySpec;
mIvParameterSpec = ivParameterSpec; }
@Override
public int read(byte[] b, int off, int len) throws IOException {
return super.read(b, off, len); }
public long forceSkip(long bytesToSkip) throws IOException {
long skipped = mUpstream.skip(bytesToSkip);
try {
int skip = (int) (bytesToSkip % AES_BLOCK_SIZE);
long blockOffset = bytesToSkip - skip;
long numberOfBlocks = blockOffset / AES_BLOCK_SIZE;
BigInteger ivForOffsetAsBigInteger = new BigInteger(1,
mIvParameterSpec.getIV()).add(BigInteger.valueOf(numberOfBlocks));
byte[] ivForOffsetByteArray = ivForOffsetAsBigInteger.toByteArray();
IvParameterSpec computedIvParameterSpecForOffset;
if (ivForOffsetByteArray.length < AES_BLOCK_SIZE) {
byte[] resizedIvForOffsetByteArray = new byte[AES_BLOCK_SIZE];
System.arraycopy(ivForOffsetByteArray, 0, resizedIvForOffsetByteArray,
AES_BLOCK_SIZE - ivForOffsetByteArray.length, ivForOffsetByteArray.length);
computedIvParameterSpecForOffset = new IvParameterSpec(resizedIvForOffsetByteArray);
} else {
computedIvParameterSpecForOffset = new IvParameterSpec(ivForOffsetByteArray, ivForOffsetByteArray.length - AES_BLOCK_SIZE, AES_BLOCK_SIZE);
}
mCipher.init(Cipher.ENCRYPT_MODE, mSecretKeySpec, computedIvParameterSpecForOffset);
byte[] skipBuffer = new byte[skip];
mCipher.update(skipBuffer, 0, skip, skipBuffer);
Arrays.fill(skipBuffer, (byte) 0);
} catch (Exception e) {
return 0;
}
return skipped;
}
@Override
public int available() throws IOException {
return mUpstream.available();}