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Diffstat (limited to 'OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/SentenceConfirm.java')
| -rw-r--r-- | OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/SentenceConfirm.java | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/SentenceConfirm.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/SentenceConfirm.java new file mode 100644 index 000000000..ead70b8f6 --- /dev/null +++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/SentenceConfirm.java @@ -0,0 +1,206 @@ +/* + * 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"); + int bits = bin.readBits(neededBits); + 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() != 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() != 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() != 0) { + sentence.append(" ").append(getWord(adv, bits)); // Adverb + } + + sentence.incBits(); + if (bits.readBit() != 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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