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