210 lines
7.2 KiB
Java
210 lines
7.2 KiB
Java
/*
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* Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
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* Copyright (C) 2014 Jake McGinty (Open Whisper Systems)
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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.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.ByteArrayInputStream;
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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.List;
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/**
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* From https://github.com/mcginty/TextSecure/tree/mnemonic-poem
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*/
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public class SentenceConfirm {
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Context context;
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List<String> n, vi, vt, adj, adv, p, art;
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public SentenceConfirm(Context context) {
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this.context = context;
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try {
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n = readFile(R.raw.fp_sentence_nouns);
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vi = readFile(R.raw.fp_sentence_verbs_i);
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vt = readFile(R.raw.fp_sentence_verbs_t);
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adj = readFile(R.raw.fp_sentence_adjectives);
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adv = readFile(R.raw.fp_sentence_adverbs);
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p = readFile(R.raw.fp_sentence_prepositions);
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art = readFile(R.raw.fp_sentence_articles);
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} catch (IOException e) {
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Log.e(Constants.TAG, "Reading sentence files failed", e);
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}
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}
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List<String> readFile(int resId) throws IOException {
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if (context.getApplicationContext() == null) {
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throw new AssertionError("app context can't be null");
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}
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BufferedReader in = new BufferedReader(new InputStreamReader(
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context.getApplicationContext()
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.getResources()
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.openRawResource(resId)));
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List<String> words = new ArrayList<>();
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String word = in.readLine();
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while (word != null) {
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words.add(word);
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word = in.readLine();
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}
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in.close();
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return words;
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}
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public String fromBytes(final byte[] bytes, int desiredBytes) throws IOException {
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BitInputStream bin = new BitInputStream(new ByteArrayInputStream(bytes));
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EntropyString fingerprint = new EntropyString();
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while (fingerprint.getBits() < (desiredBytes * 8)) {
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if (!fingerprint.isEmpty()) {
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fingerprint.append("\n\n");
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}
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try {
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fingerprint.append(getSentence(bin));
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} catch (IOException e) {
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Log.e(Constants.TAG, "IOException when creating the sentence");
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throw e;
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}
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}
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return fingerprint.toString();
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}
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/**
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* Grab a word for a list of them using the necessary bits to choose from a BitInputStream
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*
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* @param words the list of words to select from
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* @param bin the bit input stream to encode from
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* @return A Pair of the word and the number of bits consumed from the stream
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*/
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private EntropyString getWord(List<String> words, BitInputStream bin) throws IOException {
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final int neededBits = log(words.size(), 2);
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Log.d(Constants.TAG, "need: " + neededBits + " bits of entropy");
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Log.d(Constants.TAG, "available: " + bin.available() + " bits");
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if (neededBits > bin.available()) {
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Log.d(Constants.TAG, "stuffed with " + (neededBits - bin.available()) + " ones!");
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}
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int bits = bin.readBits(neededBits, true);
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Log.d(Constants.TAG, "got word " + words.get(bits) + " with " + neededBits + " bits of entropy");
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return new EntropyString(words.get(bits), neededBits);
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}
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private EntropyString getNounPhrase(BitInputStream bits) throws IOException {
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final EntropyString phrase = new EntropyString();
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phrase.append(getWord(art, bits)).append(" ");
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if (bits.readBit(true) != 0) {
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phrase.append(getWord(adj, bits)).append(" ");
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}
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phrase.incBits();
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phrase.append(getWord(n, bits));
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Log.d(Constants.TAG, "got phrase " + phrase + " with " + phrase.getBits() + " bits of entropy");
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return phrase;
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}
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EntropyString getSentence(BitInputStream bits) throws IOException {
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final EntropyString sentence = new EntropyString();
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sentence.append(getNounPhrase(bits)); // Subject
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if (bits.readBit(true) != 0) {
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sentence.append(" ").append(getWord(vt, bits)); // Transitive verb
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sentence.append(" ").append(getNounPhrase(bits)); // Object of transitive verb
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} else {
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sentence.append(" ").append(getWord(vi, bits)); // Intransitive verb
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}
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sentence.incBits();
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if (bits.readBit(true) != 0) {
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sentence.append(" ").append(getWord(adv, bits)); // Adverb
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}
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sentence.incBits();
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if (bits.readBit(true) != 0) {
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sentence.append(" ").append(getWord(p, bits)); // Preposition
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sentence.append(" ").append(getNounPhrase(bits)); // Object of preposition
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}
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sentence.incBits();
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Log.d(Constants.TAG, "got sentence '" + sentence + "' with " + sentence.getBits() + " bits of entropy");
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// uppercase first character, end with dot (without increasing the bits)
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sentence.getBuilder().replace(0, 1,
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Character.toString(Character.toUpperCase(sentence.getBuilder().charAt(0))));
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sentence.getBuilder().append(".");
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return sentence;
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}
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public static class EntropyString {
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private StringBuilder builder;
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private int bits;
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public EntropyString(String phrase, int bits) {
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this.builder = new StringBuilder(phrase);
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this.bits = bits;
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}
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public EntropyString() {
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this("", 0);
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}
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public StringBuilder getBuilder() {
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return builder;
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}
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public boolean isEmpty() {
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return builder.length() == 0;
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}
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public EntropyString append(EntropyString phrase) {
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builder.append(phrase);
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bits += phrase.getBits();
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return this;
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}
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public EntropyString append(String string) {
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builder.append(string);
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return this;
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}
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public int getBits() {
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return bits;
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}
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public void setBits(int bits) {
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this.bits = bits;
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}
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public void incBits() {
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bits += 1;
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}
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@Override
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public String toString() {
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return builder.toString();
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}
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}
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private static int log(int x, int base) {
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return (int) (Math.log(x) / Math.log(base));
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}
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} |