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/*
* This file and its header file are for translating Electrum-style word lists
* into their equivalent byte representations for cross-compatibility with
* that method of "backing up" one's wallet keys.
*/
#include <string>
#include <cassert>
#include <map>
#include <cstdint>
#include <vector>
#include <boost/algorithm/string.hpp>
#include "crypto/crypto.h" // for declaration of crypto::secret_key
#include "crypto/electrum-words.h"
namespace crypto
{
namespace ElectrumWords
{
/* convert words to bytes, 3 words -> 4 bytes
* returns:
* false if not a multiple of 3 words, or if a words is not in the
* words list
*
* true otherwise
*/
bool words_to_bytes(const std::string& words, crypto::secret_key& dst)
{
int n = NUMWORDS; // hardcoded because this is what electrum uses
std::vector<std::string> wlist;
boost::split(wlist, words, boost::is_any_of(" "));
// error on non-compliant word list
if (wlist.size() != 12 && wlist.size() != 24) return false;
for (unsigned int i=0; i < wlist.size() / 3; i++)
{
uint32_t val;
uint32_t w1, w2, w3;
// verify all three words exist in the word list
if (wordsMap.count(wlist[i*3]) == 0 ||
wordsMap.count(wlist[i*3 + 1]) == 0 ||
wordsMap.count(wlist[i*3 + 2]) == 0)
{
return false;
}
w1 = wordsMap.at(wlist[i*3]);
w2 = wordsMap.at(wlist[i*3 + 1]);
w3 = wordsMap.at(wlist[i*3 + 2]);
val = w1 + n * ((w2 - w1) % n) + n * n * ((w3 - w2) % n);
memcpy(dst.data + i * 4, &val, 4); // copy 4 bytes to position
}
std::string wlist_copy = words;
if (wlist.size() == 12)
{
memcpy(dst.data, dst.data + 16, 16); // if electrum 12-word seed, duplicate
wlist_copy += ' ';
wlist_copy += words;
}
std::string back_to_words;
bytes_to_words(dst, back_to_words);
assert(wlist_copy == back_to_words); // sanity check
return true;
}
/* convert bytes to words, 4 bytes-> 3 words
* returns:
* false if wrong number of bytes (shouldn't be possible)
* true otherwise
*/
bool bytes_to_words(const crypto::secret_key& src, std::string& words)
{
int n = NUMWORDS; // hardcoded because this is what electrum uses
if (sizeof(src.data) % 4 != 0) return false;
// 8 bytes -> 3 words. 8 digits base 16 -> 3 digits base 1626
for (unsigned int i=0; i < sizeof(src.data)/4; i++, words += ' ')
{
uint32_t w1, w2, w3;
uint32_t val;
memcpy(&val, (src.data) + (i * 4), 4);
w1 = val % n;
w2 = ((val / n) + w1) % n;
w3 = (((val / n) / n) + w2) % n;
words += wordsArray[w1];
words += ' ';
words += wordsArray[w2];
words += ' ';
words += wordsArray[w3];
}
return false;
}
} // namespace ElectrumWords
} // namespace crypto
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