I am running into an issue that I am not sure the proper fix. I used this thread as reference:
java.lang.IllegalArgumentException: bad base-64 when decrypting string
Basically I split a string into chunks and encrypt each chunk. But when it is time to decrypt the same way it never works. It always gives me this annoying exception:
"java.io.IOException: Error while finalizing cipher"
basically I split the string as below:
static public class RSAString {
private ArrayList<String> mChunkList = new ArrayList<String>();
RSAString() {
mChunkList.clear();
}
public ArrayList<String> getChunkList() {
return mChunkList;
}
RSAString(String stringSrc) {
if (stringSrc.length() < CHUNK_SIZE) {
mChunkList.add(stringSrc);
} else {
int j = 0;
for (int i = 0; i < stringSrc.length() / CHUNK_SIZE; i++) {
String subString = stringSrc.substring(j, j + CHUNK_SIZE);
mChunkList.add(subString);
j += CHUNK_SIZE;
}
int leftOver = stringSrc.length() % CHUNK_SIZE;
if (leftOver > 0) {
String subString = stringSrc.substring(j, j + leftOver);
mChunkList.add(subString);
}
}
}
}
Then I decrypt with this code:
// This **DOES NOT** work
final String AndroidOpenSSLString = "AndroidOpenSSL";
final String AndroidKeyStoreBCWorkaroundString = "AndroidKeyStoreBCWorkaround";
mProvider = Build.VERSION.SDK_INT < Build.VERSION_CODES.M ? AndroidOpenSSLString : AndroidKeyStoreBCWorkaroundString;
Cipher outCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", mProvider);
outCipher.init(Cipher.DECRYPT_MODE, mPrivateKey);
for (String chunkEncrypted : rsaEcryptedText.getChunkList()) {
byte[] cipherText = chunkEncrypted.getBytes("UTF-8");
CipherInputStream cipherInputStream = new CipherInputStream(
new ByteArrayInputStream(Base64.decode(cipherText, Base64.NO_WRAP)), 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);
}
decryptedString += new String(bytes, 0, bytes.length, "UTF-8");
cipherInputStream.close();
cipherInputStream.reset();
}
The only work around I found was to re-initialize the cypher every new sub-string. Like the hack below:
for (String chunkEncrypted : rsaEcryptedText.getChunkList()) {
// This works, but I am re-initializing the out cypher every time!
// super slow!!! WHY DO I HAVE TO DO THIS?
Cipher outCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", mProvider);
outCipher.init(Cipher.DECRYPT_MODE, mPrivateKey);
byte[] cipherText = chunkEncrypted.getBytes("UTF-8");
CipherInputStream cipherInputStream = new CipherInputStream(
new ByteArrayInputStream(Base64.decode(cipherText, Base64.NO_WRAP)), 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);
}
decryptedString += new String(bytes, 0, bytes.length, "UTF-8");
cipherInputStream.close();
cipherInputStream.reset();
}
The problem with my fix is that it makes the decryption much slower. Also, even with my sub-strings at small sizes (sub-string int CHUNK_SIZE = 64) I keep getting the same exception.
Anyway, I wonder if anyone can point me out the correct way to decrypt a long string with RSA encryption.
and here is the encryption code--not sure if it matters in this case--but it always works:
Cipher inCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", mProvider);
inCipher.init(Cipher.ENCRYPT_MODE, mPublicKey);
RSAString rsaStringPlainText = new RSAString(plainText);
for (String chunkPlain : rsaStringPlainText.getChunkList()) {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
CipherOutputStream cipherOutputStream = new CipherOutputStream(
outputStream, inCipher);
cipherOutputStream.write(chunkPlain.getBytes("UTF-8"));
cipherOutputStream.flush();
cipherOutputStream.close();
byte[] ecryptedText = Base64.encode(outputStream.toByteArray(), Base64.NO_WRAP);
encryptedStringOut.mChunkList.add(new String(ecryptedText));
}