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