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/*
* Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.sufficientlysecure.keychain.experimental;
import android.content.Context;
import org.bouncycastle.util.Arrays;
import org.sufficientlysecure.keychain.Constants;
import org.sufficientlysecure.keychain.R;
import org.sufficientlysecure.keychain.util.Log;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.BitSet;
public class WordConfirm {
public static String getWords(Context context, byte[] fingerprintBlob) {
ArrayList<String> words = new ArrayList<>();
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(
context.getResources().openRawResource(R.raw.fp_word_list),
"UTF-8"
));
String line = reader.readLine();
while (line != null) {
words.add(line);
line = reader.readLine();
}
} catch (IOException e) {
throw new RuntimeException("IOException", e);
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException ignored) {
}
}
}
String fingerprint = "";
// NOTE: 160 bit SHA-1 truncated to 156 bit
byte[] fingerprintBlobTruncated = Arrays.copyOfRange(fingerprintBlob, 0, 156 / 8);
// TODO: implement key stretching to minimize fp length?
// BitSet bits = BitSet.valueOf(fingerprintBlob); // min API 19 and little endian!
BitSet bits = bitSetToByteArray(fingerprintBlobTruncated);
Log.d(Constants.TAG, "bits: " + bits.toString());
final int CHUNK_SIZE = 13;
final int LAST_CHUNK_INDEX = fingerprintBlobTruncated.length * 8 / CHUNK_SIZE; // 12
Log.d(Constants.TAG, "LAST_CHUNK_INDEX: " + LAST_CHUNK_INDEX);
int from = 0;
int to = CHUNK_SIZE;
for (int i = 0; i < (LAST_CHUNK_INDEX + 1); i++) {
Log.d(Constants.TAG, "from: " + from + " to: " + to);
BitSet setIndex = bits.get(from, to);
int wordIndex = (int) bitSetToLong(setIndex);
// int wordIndex = (int) setIndex.toLongArray()[0]; // min API 19
fingerprint += words.get(wordIndex);
if (i != LAST_CHUNK_INDEX) {
// line break every 3 words
if (to % (CHUNK_SIZE * 3) == 0) {
fingerprint += "\n";
} else {
fingerprint += " ";
}
}
from = to;
to += CHUNK_SIZE;
}
return fingerprint;
}
/**
* Returns a BitSet containing the values in bytes.
* BIG ENDIAN!
*/
private static BitSet bitSetToByteArray(byte[] bytes) {
int arrayLength = bytes.length * 8;
BitSet bits = new BitSet();
for (int i = 0; i < arrayLength; i++) {
if ((bytes[bytes.length - i / 8 - 1] & (1 << (i % 8))) > 0) {
bits.set(i);
}
}
return bits;
}
private static long bitSetToLong(BitSet bits) {
long value = 0L;
for (int i = 0; i < bits.length(); ++i) {
value += bits.get(i) ? (1L << i) : 0L;
}
return value;
}
}
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