wallet: wipe seed from memory where appropriate

19 files changed, 653 insertions, 144 deletions

diff --git a/contrib/epee/include/fnv1.h b/contrib/epee/include/fnv1.h
new file mode 100644
index 000000000..c04389bca
--- /dev/null
+++ b/contrib/epee/include/fnv1.h
@@ -0,0 +1,45 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+namespace epee
+{
+
+namespace fnv
+{
+  inline uint64_t FNV1a(const char *ptr, size_t sz)
+  {
+    uint64_t h = 0xcbf29ce484222325;
+    for (size_t i = 0; i < sz; ++i)
+      h = (h ^ *(const uint8_t*)ptr++) * 0x100000001b3;
+    return h;
+  }
+}
+
+}
diff --git a/contrib/epee/include/hex.h b/contrib/epee/include/hex.h
index e960da1d2..02600c320 100644
--- a/contrib/epee/include/hex.h
+++ b/contrib/epee/include/hex.h
@@ -33,6 +33,7 @@
 #include <iosfwd>
 #include <string>
 
+#include "wipeable_string.h"
 #include "span.h"
 
 namespace epee
@@ -41,6 +42,8 @@ namespace epee
   {
     //! \return A std::string containing hex of `src`.
     static std::string string(const span<const std::uint8_t> src);
+    //! \return A epee::wipeable_string containing hex of `src`.
+    static epee::wipeable_string wipeable_string(const span<const std::uint8_t> src);
 
     //! \return An array containing hex of `src`.
     template<std::size_t N>
@@ -59,6 +62,8 @@ namespace epee
     static void formatted(std::ostream& out, const span<const std::uint8_t> src);
 
   private:
+    template<typename T> T static convert(const span<const std::uint8_t> src);
+
     //! Write `src` bytes as hex to `out`. `out` must be twice the length
     static void buffer_unchecked(char* out, const span<const std::uint8_t> src) noexcept;
   };
diff --git a/contrib/epee/include/wipeable_string.h b/contrib/epee/include/wipeable_string.h
index 70d1a9586..4cebe5fdf 100644
--- a/contrib/epee/include/wipeable_string.h
+++ b/contrib/epee/include/wipeable_string.h
@@ -28,28 +28,43 @@
 
 #pragma once
 
+#include <boost/optional/optional_fwd.hpp>
 #include <stddef.h>
 #include <vector>
 #include <string>
+#include "fnv1.h"
 
 namespace epee
 {
   class wipeable_string
   {
   public:
+    typedef char value_type;
+
     wipeable_string() {}
     wipeable_string(const wipeable_string &other);
     wipeable_string(wipeable_string &&other);
     wipeable_string(const std::string &other);
     wipeable_string(std::string &&other);
     wipeable_string(const char *s);
+    wipeable_string(const char *s, size_t len);
     ~wipeable_string();
     void wipe();
     void push_back(char c);
-    void pop_back();
+    void operator+=(char c);
+    void operator+=(const std::string &s);
+    void operator+=(const epee::wipeable_string &s);
+    void operator+=(const char *s);
+    void append(const char *ptr, size_t len);
+    char pop_back();
     const char *data() const noexcept { return buffer.data(); }
+    char *data() noexcept { return buffer.data(); }
     size_t size() const noexcept { return buffer.size(); }
+    size_t length() const noexcept { return buffer.size(); }
     bool empty() const noexcept { return buffer.empty(); }
+    void trim();
+    void split(std::vector<wipeable_string> &fields) const;
+    boost::optional<wipeable_string> parse_hexstr() const;
     void resize(size_t sz);
     void reserve(size_t sz);
     void clear();
@@ -65,3 +80,14 @@ namespace epee
     std::vector<char> buffer;
   };
 }
+
+namespace std
+{
+  template<> struct hash<epee::wipeable_string>
+  {
+    size_t operator()(const epee::wipeable_string &s) const
+    {
+      return epee::fnv::FNV1a(s.data(), s.size());
+    }
+  };
+}
diff --git a/contrib/epee/src/hex.cpp b/contrib/epee/src/hex.cpp
index c143b2dc2..5c8acc8be 100644
--- a/contrib/epee/src/hex.cpp
+++ b/contrib/epee/src/hex.cpp
@@ -52,17 +52,21 @@ namespace epee
     }
   }
 
-  std::string to_hex::string(const span<const std::uint8_t> src)
+  template<typename T>
+  T to_hex::convert(const span<const std::uint8_t> src)
   {
     if (std::numeric_limits<std::size_t>::max() / 2 < src.size())
       throw std::range_error("hex_view::to_string exceeded maximum size");
 
-    std::string out{};
+    T out{};
     out.resize(src.size() * 2);
-    buffer_unchecked(std::addressof(out[0]), src);
+    to_hex::buffer_unchecked((char*)out.data(), src); // can't see the non const version in wipeable_string??
     return out;
   }
 
+  std::string to_hex::string(const span<const std::uint8_t> src) { return convert<std::string>(src); }
+  epee::wipeable_string to_hex::wipeable_string(const span<const std::uint8_t> src) { return convert<epee::wipeable_string>(src); }
+
   void to_hex::buffer(std::ostream& out, const span<const std::uint8_t> src)
   {
     write_hex(std::ostreambuf_iterator<char>{out}, src);
diff --git a/contrib/epee/src/wipeable_string.cpp b/contrib/epee/src/wipeable_string.cpp
index 6ed4ee8a2..7c9722765 100644
--- a/contrib/epee/src/wipeable_string.cpp
+++ b/contrib/epee/src/wipeable_string.cpp
@@ -26,11 +26,22 @@
 // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#include <boost/optional/optional.hpp>
 #include <string.h>
 #include "memwipe.h"
 #include "misc_log_ex.h"
 #include "wipeable_string.h"
 
+namespace
+{
+  int atolower(int c)
+  {
+    if (c >= 'A' && c <= 'Z')
+      c |= 32;
+    return c;
+  }
+}
+
 namespace epee
 {
 
@@ -69,6 +80,12 @@ wipeable_string::wipeable_string(const char *s)
   memcpy(buffer.data(), s, size());
 }
 
+wipeable_string::wipeable_string(const char *s, size_t len)
+{
+  grow(len);
+  memcpy(buffer.data(), s, len);
+}
+
 wipeable_string::~wipeable_string()
 {
   wipe();
@@ -109,9 +126,100 @@ void wipeable_string::push_back(char c)
   buffer.back() = c;
 }
 
-void wipeable_string::pop_back()
+void wipeable_string::operator+=(char c)
+{
+  push_back(c);
+}
+
+void wipeable_string::append(const char *ptr, size_t len)
+{
+  const size_t orgsz = size();
+  CHECK_AND_ASSERT_THROW_MES(orgsz < std::numeric_limits<size_t>::max() - len, "Appended data too large");
+  grow(orgsz + len);
+  if (len > 0)
+    memcpy(data() + orgsz, ptr, len);
+}
+
+void wipeable_string::operator+=(const char *s)
+{
+  append(s, strlen(s));
+}
+
+void wipeable_string::operator+=(const epee::wipeable_string &s)
+{
+  append(s.data(), s.size());
+}
+
+void wipeable_string::operator+=(const std::string &s)
+{
+  append(s.c_str(), s.size());
+}
+
+void wipeable_string::trim()
+{
+  size_t prefix = 0;
+  while (prefix < size() && data()[prefix] == ' ')
+    ++prefix;
+  if (prefix > 0)
+    memmove(buffer.data(), buffer.data() + prefix, size() - prefix);
+
+  size_t suffix = 0;
+  while (suffix < size()-prefix && data()[size() - 1 - prefix - suffix] == ' ')
+    ++suffix;
+
+  resize(size() - prefix - suffix);
+}
+
+void wipeable_string::split(std::vector<wipeable_string> &fields) const
+{
+  fields.clear();
+  size_t len = size();
+  const char *ptr = data();
+  bool space = true;
+  while (len--)
+  {
+    const char c = *ptr++;
+    if (c != ' ')
+    {
+      if (space)
+        fields.push_back({});
+      fields.back().push_back(c);
+    }
+    space = c == ' ';
+  }
+}
+
+boost::optional<epee::wipeable_string> wipeable_string::parse_hexstr() const
+{
+  if (size() % 2 != 0)
+    return boost::none;
+  boost::optional<epee::wipeable_string> res = epee::wipeable_string("");
+  const size_t len = size();
+  const char *d = data();
+  res->grow(0, len / 2);
+  static constexpr const char hex[] = u8"0123456789abcdef";
+  for (size_t i = 0; i < len; i += 2)
+  {
+    char c = atolower(d[i]);
+    const char *ptr0 = strchr(hex, c);
+    if (!ptr0)
+      return boost::none;
+    c = atolower(d[i+1]);
+    const char *ptr1 = strchr(hex, c);
+    if (!ptr1)
+      return boost::none;
+    res->push_back(((ptr0-hex)<<4) | (ptr1-hex));
+  }
+  return res;
+}
+
+char wipeable_string::pop_back()
 {
-  resize(size() - 1);
+  const size_t sz = size();
+  CHECK_AND_ASSERT_THROW_MES(sz > 0, "Popping from an empty string");
+  const char c = buffer.back();
+  resize(sz - 1);
+  return c;
 }
 
 void wipeable_string::resize(size_t sz)
diff --git a/src/common/password.cpp b/src/common/password.cpp
index 3ce2ba42a..5671c4a4e 100644
--- a/src/common/password.cpp
+++ b/src/common/password.cpp
@@ -54,7 +54,7 @@ namespace
     return 0 != _isatty(_fileno(stdin));
   }
 
-  bool read_from_tty(epee::wipeable_string& pass)
+  bool read_from_tty(epee::wipeable_string& pass, bool hide_input)
   {
     static constexpr const char BACKSPACE = 8;
 
@@ -62,7 +62,7 @@ namespace
 
     DWORD mode_old;
     ::GetConsoleMode(h_cin, &mode_old);
-    DWORD mode_new = mode_old & ~(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT);
+    DWORD mode_new = mode_old & ~((hide_input ? ENABLE_ECHO_INPUT : 0) | ENABLE_LINE_INPUT);
     ::SetConsoleMode(h_cin, mode_new);
 
     bool r = true;
@@ -107,14 +107,14 @@ namespace
     return 0 != isatty(fileno(stdin));
   }
 
-  int getch() noexcept
+  int getch(bool hide_input) noexcept
   {
     struct termios tty_old;
     tcgetattr(STDIN_FILENO, &tty_old);
 
     struct termios tty_new;
     tty_new = tty_old;
-    tty_new.c_lflag &= ~(ICANON | ECHO);
+    tty_new.c_lflag &= ~(ICANON | (hide_input ? ECHO : 0));
     tcsetattr(STDIN_FILENO, TCSANOW, &tty_new);
 
     int ch = getchar();
@@ -124,14 +124,14 @@ namespace
     return ch;
   }
 
-  bool read_from_tty(epee::wipeable_string& aPass)
+  bool read_from_tty(epee::wipeable_string& aPass, bool hide_input)
   {
     static constexpr const char BACKSPACE = 127;
 
     aPass.reserve(tools::password_container::max_password_size);
     while (aPass.size() < tools::password_container::max_password_size)
     {
-      int ch = getch();
+      int ch = getch(hide_input);
       if (EOF == ch || ch == EOT)
       {
         return false;
@@ -159,18 +159,18 @@ namespace
 
 #endif // end !WIN32
 
-  bool read_from_tty(const bool verify, const char *message, epee::wipeable_string& pass1, epee::wipeable_string& pass2)
+  bool read_from_tty(const bool verify, const char *message, bool hide_input, epee::wipeable_string& pass1, epee::wipeable_string& pass2)
   {
     while (true)
     {
       if (message)
         std::cout << message <<": " << std::flush;
-      if (!read_from_tty(pass1))
+      if (!read_from_tty(pass1, hide_input))
         return false;
       if (verify)
       {
         std::cout << "Confirm password: ";
-        if (!read_from_tty(pass2))
+        if (!read_from_tty(pass2, hide_input))
           return false;
         if(pass1!=pass2)
         {
@@ -229,12 +229,12 @@ namespace tools
 
   std::atomic<bool> password_container::is_prompting(false);
 
-  boost::optional<password_container> password_container::prompt(const bool verify, const char *message)
+  boost::optional<password_container> password_container::prompt(const bool verify, const char *message, bool hide_input)
   {
     is_prompting = true;
     password_container pass1{};
     password_container pass2{};
-    if (is_cin_tty() ? read_from_tty(verify, message, pass1.m_password, pass2.m_password) : read_from_file(pass1.m_password))
+    if (is_cin_tty() ? read_from_tty(verify, message, hide_input, pass1.m_password, pass2.m_password) : read_from_file(pass1.m_password))
     {
       is_prompting = false;
       return {std::move(pass1)};
diff --git a/src/common/password.h b/src/common/password.h
index 61937b93a..529881e40 100644
--- a/src/common/password.h
+++ b/src/common/password.h
@@ -49,7 +49,7 @@ namespace tools
     password_container(std::string&& password) noexcept;
 
     //! \return A password from stdin TTY prompt or `std::cin` pipe.
-    static boost::optional<password_container> prompt(bool verify, const char *mesage = "Password");
+    static boost::optional<password_container> prompt(bool verify, const char *mesage = "Password", bool hide_input = true);
     static std::atomic<bool> is_prompting;
 
     password_container(const password_container&) = delete;
diff --git a/src/mnemonics/electrum-words.cpp b/src/mnemonics/electrum-words.cpp
index 19a9c26bb..290f2cb93 100644
--- a/src/mnemonics/electrum-words.cpp
+++ b/src/mnemonics/electrum-words.cpp
@@ -43,6 +43,8 @@
 #include <vector>
 #include <unordered_map>
 #include <boost/algorithm/string.hpp>
+#include "wipeable_string.h"
+#include "misc_language.h"
 #include "crypto/crypto.h"  // for declaration of crypto::secret_key
 #include <fstream>
 #include "mnemonics/electrum-words.h"
@@ -80,9 +82,9 @@ namespace crypto
 
 namespace
 {
-  uint32_t create_checksum_index(const std::vector<std::string> &word_list,
+  uint32_t create_checksum_index(const std::vector<epee::wipeable_string> &word_list,
     uint32_t unique_prefix_length);
-  bool checksum_test(std::vector<std::string> seed, uint32_t unique_prefix_length);
+  bool checksum_test(std::vector<epee::wipeable_string> seed, uint32_t unique_prefix_length);
 
   /*!
    * \brief Finds the word list that contains the seed words and puts the indices
@@ -93,7 +95,7 @@ namespace
    * \param  language        Language instance pointer to write to after it is found.
    * \return                 true if all the words were present in some language false if not.
    */
-  bool find_seed_language(const std::vector<std::string> &seed,
+  bool find_seed_language(const std::vector<epee::wipeable_string> &seed,
     bool has_checksum, std::vector<uint32_t> &matched_indices, Language::Base **language)
   {
     // If there's a new language added, add an instance of it here.
@@ -114,17 +116,19 @@ namespace
     });
     Language::Base *fallback = NULL;
 
+    std::vector<epee::wipeable_string>::const_iterator it2;
+    matched_indices.reserve(seed.size());
+
     // Iterate through all the languages and find a match
     for (std::vector<Language::Base*>::iterator it1 = language_instances.begin();
       it1 != language_instances.end(); it1++)
     {
-      const std::unordered_map<std::string, uint32_t> &word_map = (*it1)->get_word_map();
-      const std::unordered_map<std::string, uint32_t> &trimmed_word_map = (*it1)->get_trimmed_word_map();
+      const std::unordered_map<epee::wipeable_string, uint32_t> &word_map = (*it1)->get_word_map();
+      const std::unordered_map<epee::wipeable_string, uint32_t> &trimmed_word_map = (*it1)->get_trimmed_word_map();
       // To iterate through seed words
-      std::vector<std::string>::const_iterator it2;
       bool full_match = true;
 
-      std::string trimmed_word;
+      epee::wipeable_string trimmed_word;
       // Iterate through all the words and see if they're all present
       for (it2 = seed.begin(); it2 != seed.end(); it2++)
       {
@@ -167,6 +171,7 @@ namespace
         return true;
       }
       // Some didn't match. Clear the index array.
+      memwipe(matched_indices.data(), matched_indices.size() * sizeof(matched_indices[0]));
       matched_indices.clear();
     }
 
@@ -181,6 +186,7 @@ namespace
     }
 
     MINFO("No match found");
+    memwipe(matched_indices.data(), matched_indices.size() * sizeof(matched_indices[0]));
     return false;
   }
 
@@ -190,12 +196,12 @@ namespace
    * \param unique_prefix_length  the prefix length of each word to use for checksum
    * \return                      Checksum index
    */
-  uint32_t create_checksum_index(const std::vector<std::string> &word_list,
+  uint32_t create_checksum_index(const std::vector<epee::wipeable_string> &word_list,
     uint32_t unique_prefix_length)
   {
-    std::string trimmed_words = "";
+    epee::wipeable_string trimmed_words = "";
 
-    for (std::vector<std::string>::const_iterator it = word_list.begin(); it != word_list.end(); it++)
+    for (std::vector<epee::wipeable_string>::const_iterator it = word_list.begin(); it != word_list.end(); it++)
     {
       if (it->length() > unique_prefix_length)
       {
@@ -217,22 +223,22 @@ namespace
    * \param unique_prefix_length  the prefix length of each word to use for checksum
    * \return                      True if the test passed false if not.
    */
-  bool checksum_test(std::vector<std::string> seed, uint32_t unique_prefix_length)
+  bool checksum_test(std::vector<epee::wipeable_string> seed, uint32_t unique_prefix_length)
   {
     if (seed.empty())
       return false;
     // The last word is the checksum.
-    std::string last_word = seed.back();
+    epee::wipeable_string last_word = seed.back();
     seed.pop_back();
 
-    std::string checksum = seed[create_checksum_index(seed, unique_prefix_length)];
+    epee::wipeable_string checksum = seed[create_checksum_index(seed, unique_prefix_length)];
 
-    std::string trimmed_checksum = checksum.length() > unique_prefix_length ? Language::utf8prefix(checksum, unique_prefix_length) :
+    epee::wipeable_string trimmed_checksum = checksum.length() > unique_prefix_length ? Language::utf8prefix(checksum, unique_prefix_length) :
       checksum;
-    std::string trimmed_last_word = last_word.length() > unique_prefix_length ? Language::utf8prefix(last_word, unique_prefix_length) :
+    epee::wipeable_string trimmed_last_word = last_word.length() > unique_prefix_length ? Language::utf8prefix(last_word, unique_prefix_length) :
       last_word;
     bool ret = trimmed_checksum == trimmed_last_word;
-    MINFO("Checksum is %s" << (ret ? "valid" : "invalid"));
+    MINFO("Checksum is " << (ret ? "valid" : "invalid"));
     return ret;
   }
 }
@@ -260,13 +266,12 @@ namespace crypto
      * \param  language_name   Language of the seed as found gets written here.
      * \return                 false if not a multiple of 3 words, or if word is not in the words list
      */
-    bool words_to_bytes(std::string words, std::string& dst, size_t len, bool duplicate,
+    bool words_to_bytes(const epee::wipeable_string &words, epee::wipeable_string& dst, size_t len, bool duplicate,
       std::string &language_name)
     {
-      std::vector<std::string> seed;
+      std::vector<epee::wipeable_string> seed;
 
-      boost::algorithm::trim(words);
-      boost::split(seed, words, boost::is_any_of(" "), boost::token_compress_on);
+      words.split(seed);
 
       if (len % 4)
       {
@@ -291,6 +296,7 @@ namespace crypto
       }
 
       std::vector<uint32_t> matched_indices;
+      auto wiper = epee::misc_utils::create_scope_leave_handler([&](){memwipe(matched_indices.data(), matched_indices.size() * sizeof(matched_indices[0]));});
       Language::Base *language;
       if (!find_seed_language(seed, has_checksum, matched_indices, &language))
       {
@@ -313,33 +319,33 @@ namespace crypto
 
       for (unsigned int i=0; i < seed.size() / 3; i++)
       {
-        uint32_t val;
-        uint32_t w1, w2, w3;
-        w1 = matched_indices[i*3];
-        w2 = matched_indices[i*3 + 1];
-        w3 = matched_indices[i*3 + 2];
+        uint32_t w[4];
+        w[1] = matched_indices[i*3];
+        w[2] = matched_indices[i*3 + 1];
+        w[3] = matched_indices[i*3 + 2];
 
-        val = w1 + word_list_length * (((word_list_length - w1) + w2) % word_list_length) +
-          word_list_length * word_list_length * (((word_list_length - w2) + w3) % word_list_length);
+        w[0]= w[1] + word_list_length * (((word_list_length - w[1]) + w[2]) % word_list_length) +
+          word_list_length * word_list_length * (((word_list_length - w[2]) + w[3]) % word_list_length);
 
-        if (!(val % word_list_length == w1))
+        if (!(w[0]% word_list_length == w[1]))
         {
+          memwipe(w, sizeof(w));
           MERROR("Invalid seed: mumble mumble");
           return false;
         }
 
-        dst.append((const char*)&val, 4);  // copy 4 bytes to position
+        dst.append((const char*)&w[0], 4);  // copy 4 bytes to position
+        memwipe(w, sizeof(w));
       }
 
       if (len > 0 && duplicate)
       {
         const size_t expected = len * 3 / 32;
-        std::string wlist_copy = words;
         if (seed.size() == expected/2)
         {
-          dst.append(dst);                    // if electrum 12-word seed, duplicate
-          wlist_copy += ' ';
-          wlist_copy += words;
+          dst += ' ';                    // if electrum 12-word seed, duplicate
+          dst += dst;                    // if electrum 12-word seed, duplicate
+          dst.pop_back();                // trailing space
         }
       }
 
@@ -353,10 +359,10 @@ namespace crypto
      * \param  language_name   Language of the seed as found gets written here.
      * \return                 false if not a multiple of 3 words, or if word is not in the words list
      */
-    bool words_to_bytes(std::string words, crypto::secret_key& dst,
+    bool words_to_bytes(const epee::wipeable_string &words, crypto::secret_key& dst,
       std::string &language_name)
     {
-      std::string s;
+      epee::wipeable_string s;
       if (!words_to_bytes(words, s, sizeof(dst), true, language_name))
       {
         MERROR("Invalid seed: failed to convert words to bytes");
@@ -378,7 +384,7 @@ namespace crypto
      * \param  language_name Seed language name
      * \return               true if successful false if not. Unsuccessful if wrong key size.
      */
-    bool bytes_to_words(const char *src, size_t len, std::string& words,
+    bool bytes_to_words(const char *src, size_t len, epee::wipeable_string& words,
       const std::string &language_name)
     {
 
@@ -397,39 +403,38 @@ namespace crypto
       }
       const std::vector<std::string> &word_list = language->get_word_list();
       // To store the words for random access to add the checksum word later.
-      std::vector<std::string> words_store;
+      std::vector<epee::wipeable_string> words_store;
 
       uint32_t word_list_length = word_list.size();
       // 4 bytes -> 3 words.  8 digits base 16 -> 3 digits base 1626
-      for (unsigned int i=0; i < len/4; i++, words += ' ')
+      for (unsigned int i=0; i < len/4; i++, words.push_back(' '))
       {
-        uint32_t w1, w2, w3;
-        
-        uint32_t val;
+        uint32_t w[4];
 
-        memcpy(&val, src + (i * 4), 4);
+        memcpy(&w[0], src + (i * 4), 4);
 
-        w1 = val % word_list_length;
-        w2 = ((val / word_list_length) + w1) % word_list_length;
-        w3 = (((val / word_list_length) / word_list_length) + w2) % word_list_length;
+        w[1] = w[0] % word_list_length;
+        w[2] = ((w[0] / word_list_length) + w[1]) % word_list_length;
+        w[3] = (((w[0] / word_list_length) / word_list_length) + w[2]) % word_list_length;
 
-        words += word_list[w1];
+        words += word_list[w[1]];
         words += ' ';
-        words += word_list[w2];
+        words += word_list[w[2]];
         words += ' ';
-        words += word_list[w3];
+        words += word_list[w[3]];
+
+        words_store.push_back(word_list[w[1]]);
+        words_store.push_back(word_list[w[2]]);
+        words_store.push_back(word_list[w[3]]);
 
-        words_store.push_back(word_list[w1]);
-        words_store.push_back(word_list[w2]);
-        words_store.push_back(word_list[w3]);
+        memwipe(w, sizeof(w));
       }
 
-      words.pop_back();
-      words += (' ' + words_store[create_checksum_index(words_store, language->get_unique_prefix_length())]);
+      words += words_store[create_checksum_index(words_store, language->get_unique_prefix_length())];
       return true;
     }
 
-    bool bytes_to_words(const crypto::secret_key& src, std::string& words,
+    bool bytes_to_words(const crypto::secret_key& src, epee::wipeable_string& words,
       const std::string &language_name)
     {
       return bytes_to_words(src.data, sizeof(src), words, language_name);
@@ -473,11 +478,10 @@ namespace crypto
      * \param  seed The seed to check (a space delimited concatenated word list)
      * \return      true if the seed passed is a old style seed false if not.
      */
-    bool get_is_old_style_seed(std::string seed)
+    bool get_is_old_style_seed(const epee::wipeable_string &seed)
     {
-      std::vector<std::string> word_list;
-      boost::algorithm::trim(seed);
-      boost::split(word_list, seed, boost::is_any_of(" "), boost::token_compress_on);
+      std::vector<epee::wipeable_string> word_list;
+      seed.split(word_list);
       return word_list.size() != (seed_length + 1);
     }
 
diff --git a/src/mnemonics/electrum-words.h b/src/mnemonics/electrum-words.h
index 856edb92a..5401b9779 100644
--- a/src/mnemonics/electrum-words.h
+++ b/src/mnemonics/electrum-words.h
@@ -44,6 +44,8 @@
 #include <map>
 #include "crypto/crypto.h"  // for declaration of crypto::secret_key
 
+namespace epee {  class wipeable_string; }
+
 /*!
  * \namespace crypto
  * 
@@ -70,7 +72,7 @@ namespace crypto
      * \param  language_name   Language of the seed as found gets written here.
      * \return                 false if not a multiple of 3 words, or if word is not in the words list
      */
-    bool words_to_bytes(std::string words, std::string& dst, size_t len, bool duplicate,
+    bool words_to_bytes(const epee::wipeable_string &words, epee::wipeable_string& dst, size_t len, bool duplicate,
       std::string &language_name);
     /*!
      * \brief Converts seed words to bytes (secret key).
@@ -79,7 +81,7 @@ namespace crypto
      * \param  language_name   Language of the seed as found gets written here.
      * \return                 false if not a multiple of 3 words, or if word is not in the words list
      */
-    bool words_to_bytes(std::string words, crypto::secret_key& dst,
+    bool words_to_bytes(const epee::wipeable_string &words, crypto::secret_key& dst,
       std::string &language_name);
 
     /*!
@@ -90,7 +92,7 @@ namespace crypto
      * \param  language_name Seed language name
      * \return               true if successful false if not. Unsuccessful if wrong key size.
      */
-    bool bytes_to_words(const char *src, size_t len, std::string& words,
+    bool bytes_to_words(const char *src, size_t len, epee::wipeable_string& words,
       const std::string &language_name);
 
     /*!
@@ -100,7 +102,7 @@ namespace crypto
      * \param  language_name Seed language name
      * \return               true if successful false if not. Unsuccessful if wrong key size.
      */
-    bool bytes_to_words(const crypto::secret_key& src, std::string& words,
+    bool bytes_to_words(const crypto::secret_key& src, epee::wipeable_string& words,
       const std::string &language_name);
 
     /*!
@@ -115,7 +117,7 @@ namespace crypto
      * \param  seed The seed to check (a space delimited concatenated word list)
      * \return      true if the seed passed is a old style seed false if not.
      */
-    bool get_is_old_style_seed(std::string seed);
+    bool get_is_old_style_seed(const epee::wipeable_string &seed);
 
     /*!
      * \brief Returns the name of a language in English
diff --git a/src/mnemonics/language_base.h b/src/mnemonics/language_base.h
index 2b0c37c6b..cf518ab2a 100644
--- a/src/mnemonics/language_base.h
+++ b/src/mnemonics/language_base.h
@@ -53,15 +53,20 @@ namespace Language
    * \param  count           How many characters to return.

    * \return                 A string consisting of the first count characters in s.

    */

-  inline std::string utf8prefix(const std::string &s, size_t count)

+  template<typename T>

+  inline T utf8prefix(const T &s, size_t count)

   {

-    std::string prefix = "";

-    const char *ptr = s.c_str();

-    while (count-- && *ptr)

+    T prefix = "";

+    size_t avail = s.size();

+    const char *ptr = s.data();

+    while (count-- && avail--)

     {

       prefix += *ptr++;

-      while (((*ptr) & 0xc0) == 0x80)

+      while (avail && ((*ptr) & 0xc0) == 0x80)

+      {

         prefix += *ptr++;

+        --avail;

+      }

     }

     return prefix;

   }

@@ -79,8 +84,8 @@ namespace Language
       ALLOW_DUPLICATE_PREFIXES = 1<<1,

     };

     const std::vector<std::string> word_list; /*!< A pointer to the array of words */

-    std::unordered_map<std::string, uint32_t> word_map; /*!< hash table to find word's index */

-    std::unordered_map<std::string, uint32_t> trimmed_word_map; /*!< hash table to find word's trimmed index */

+    std::unordered_map<epee::wipeable_string, uint32_t> word_map; /*!< hash table to find word's index */

+    std::unordered_map<epee::wipeable_string, uint32_t> trimmed_word_map; /*!< hash table to find word's trimmed index */

     std::string language_name; /*!< Name of language */

     std::string english_language_name; /*!< Name of language */

     uint32_t unique_prefix_length; /*!< Number of unique starting characters to trim the wordlist to when matching */

@@ -103,7 +108,7 @@ namespace Language
           else

             throw std::runtime_error("Too short word in " + language_name + " word list: " + *it);

         }

-        std::string trimmed;

+        epee::wipeable_string trimmed;

         if (it->length() > unique_prefix_length)

         {

           trimmed = utf8prefix(*it, unique_prefix_length);

@@ -115,9 +120,9 @@ namespace Language
         if (trimmed_word_map.find(trimmed) != trimmed_word_map.end())

         {

           if (flags & ALLOW_DUPLICATE_PREFIXES)

-            MWARNING("Duplicate prefix in " << language_name << " word list: " << trimmed);

+            MWARNING("Duplicate prefix in " << language_name << " word list: " << std::string(trimmed.data(), trimmed.size()));

           else

-            throw std::runtime_error("Duplicate prefix in " + language_name + " word list: " + trimmed);

+            throw std::runtime_error("Duplicate prefix in " + language_name + " word list: " + std::string(trimmed.data(), trimmed.size()));

         }

         trimmed_word_map[trimmed] = ii;

       }

@@ -145,7 +150,7 @@ namespace Language
      * \brief Returns a pointer to the word map.

      * \return A pointer to the word map.

      */

-    const std::unordered_map<std::string, uint32_t>& get_word_map() const

+    const std::unordered_map<epee::wipeable_string, uint32_t>& get_word_map() const

     {

       return word_map;

     }

@@ -153,7 +158,7 @@ namespace Language
      * \brief Returns a pointer to the trimmed word map.

      * \return A pointer to the trimmed word map.

      */

-    const std::unordered_map<std::string, uint32_t>& get_trimmed_word_map() const

+    const std::unordered_map<epee::wipeable_string, uint32_t>& get_trimmed_word_map() const

     {

       return trimmed_word_map;

     }

diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index e07c7e49b..f87c2936d 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -152,12 +152,31 @@ namespace
   //
   // Note also that input for passwords is NOT translated, to remain compatible with any
   // passwords containing special characters that predate this switch to UTF-8 support.
-  static std::string cp850_to_utf8(const std::string &cp850_str)
+  template<typename T>
+  static T cp850_to_utf8(const T &cp850_str)
   {
     boost::locale::generator gen;
     gen.locale_cache_enabled(true);
     std::locale loc = gen("en_US.CP850");
-    return boost::locale::conv::to_utf<char>(cp850_str, loc);
+    const boost::locale::conv::method_type how = boost::locale::conv::default_method;
+    T result;
+    const char *begin = cp850_str.data();
+    const char *end = begin + cp850_str.size();
+    result.reserve(end-begin);
+    typedef std::back_insert_iterator<T> inserter_type;
+    inserter_type inserter(result);
+    boost::locale::utf::code_point c;
+    while(begin!=end) {
+        c=boost::locale::utf::utf_traits<char>::template decode<char const *>(begin,end);
+        if(c==boost::locale::utf::illegal || c==boost::locale::utf::incomplete) {
+            if(how==boost::locale::conv::stop)
+                throw boost::locale::conv::conversion_error();
+        }
+        else {
+            boost::locale::utf::utf_traits<char>::template encode<inserter_type>(c,inserter);
+        }
+    }
+    return result;
   }
 #endif
 
@@ -177,6 +196,28 @@ namespace
     return epee::string_tools::trim(buf);
   }
 
+  epee::wipeable_string input_secure_line(const std::string& prompt)
+  {
+#ifdef HAVE_READLINE
+    rdln::suspend_readline pause_readline;
+#endif
+    auto pwd_container = tools::password_container::prompt(false, prompt.c_str(), false);
+    if (!pwd_container)
+    {
+      MERROR("Failed to read secure line");
+      return "";
+    }
+
+    epee::wipeable_string buf = pwd_container->password();
+
+#ifdef WIN32
+    buf = cp850_to_utf8(buf);
+#endif
+
+    buf.trim();
+    return buf;
+  }
+
   boost::optional<tools::password_container> password_prompter(const char *prompt, bool verify)
   {
 #ifdef HAVE_READLINE
@@ -595,7 +636,7 @@ bool simple_wallet::spendkey(const std::vector<std::string> &args/* = std::vecto
 bool simple_wallet::print_seed(bool encrypted)
 {
   bool success =  false;
-  std::string seed;
+  epee::wipeable_string seed;
   bool ready, multisig;
 
   if (m_wallet->key_on_device())
@@ -2679,28 +2720,45 @@ bool simple_wallet::ask_wallet_create_if_needed()
  * \brief Prints the seed with a nice message
  * \param seed seed to print
  */
-void simple_wallet::print_seed(std::string seed)
+void simple_wallet::print_seed(const epee::wipeable_string &seed)
 {
   success_msg_writer(true) << "\n" << tr("NOTE: the following 25 words can be used to recover access to your wallet. "
     "Write them down and store them somewhere safe and secure. Please do not store them in "
     "your email or on file storage services outside of your immediate control.\n");
-  boost::replace_nth(seed, " ", 15, "\n");
-  boost::replace_nth(seed, " ", 7, "\n");
   // don't log
-  std::cout << seed << std::endl;
+  int space_index = 0;
+  size_t len  = seed.size();
+  for (const char *ptr = seed.data(); len--; ++ptr)
+  {
+    if (*ptr == ' ')
+    {
+      if (space_index == 15 || space_index == 7)
+        putchar('\n');
+      else
+        putchar(*ptr);
+      ++space_index;
+    }
+    else
+      putchar(*ptr);
+  }
+  putchar('\n');
+  fflush(stdout);
 }
 //----------------------------------------------------------------------------------------------------
-static bool might_be_partial_seed(std::string words)
+static bool might_be_partial_seed(const epee::wipeable_string &words)
 {
-  std::vector<std::string> seed;
+  std::vector<epee::wipeable_string> seed;
 
-  boost::algorithm::trim(words);
-  boost::split(seed, words, boost::is_any_of(" "), boost::token_compress_on);
+  words.split(seed);
   return seed.size() < 24;
 }
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::init(const boost::program_options::variables_map& vm)
 {
+  epee::misc_utils::auto_scope_leave_caller scope_exit_handler = epee::misc_utils::create_scope_leave_handler([&](){
+    m_electrum_seed.wipe();
+  });
+
   const bool testnet = tools::wallet2::has_testnet_option(vm);
   const bool stagenet = tools::wallet2::has_stagenet_option(vm);
   if (testnet && stagenet)
@@ -2710,7 +2768,7 @@ bool simple_wallet::init(const boost::program_options::variables_map& vm)
   }
   const network_type nettype = testnet ? TESTNET : stagenet ? STAGENET : MAINNET;
 
-  std::string multisig_keys;
+  epee::wipeable_string multisig_keys;
 
   if (!handle_command_line(vm))
     return false;
@@ -2752,8 +2810,8 @@ bool simple_wallet::init(const boost::program_options::variables_map& vm)
       {
         if (m_restore_multisig_wallet)
         {
-            const char *prompt = "Specify multisig seed: ";
-            m_electrum_seed = input_line(prompt);
+            const char *prompt = "Specify multisig seed";
+            m_electrum_seed = input_secure_line(prompt);
             if (std::cin.eof())
               return false;
             if (m_electrum_seed.empty())
@@ -2767,8 +2825,8 @@ bool simple_wallet::init(const boost::program_options::variables_map& vm)
           m_electrum_seed = "";
           do
           {
-            const char *prompt = m_electrum_seed.empty() ? "Specify Electrum seed: " : "Electrum seed continued: ";
-            std::string electrum_seed = input_line(prompt);
+            const char *prompt = m_electrum_seed.empty() ? "Specify Electrum seed" : "Electrum seed continued";
+            epee::wipeable_string electrum_seed = input_secure_line(prompt);
             if (std::cin.eof())
               return false;
             if (electrum_seed.empty())
@@ -2776,18 +2834,21 @@ bool simple_wallet::init(const boost::program_options::variables_map& vm)
               fail_msg_writer() << tr("specify a recovery parameter with the --electrum-seed=\"words list here\"");
               return false;
             }
-            m_electrum_seed += electrum_seed + " ";
+            m_electrum_seed += electrum_seed;
+            m_electrum_seed += ' ';
           } while (might_be_partial_seed(m_electrum_seed));
         }
       }
 
       if (m_restore_multisig_wallet)
       {
-        if (!epee::string_tools::parse_hexstr_to_binbuff(m_electrum_seed, multisig_keys))
+        const boost::optional<epee::wipeable_string> parsed = m_electrum_seed.parse_hexstr();
+        if (!parsed)
         {
           fail_msg_writer() << tr("Multisig seed failed verification");
           return false;
         }
+        multisig_keys = *parsed;
       }
       else
       {
@@ -2809,7 +2870,7 @@ bool simple_wallet::init(const boost::program_options::variables_map& vm)
           crypto::secret_key key;
           crypto::cn_slow_hash(seed_pass.data(), seed_pass.size(), (crypto::hash&)key);
           sc_reduce32((unsigned char*)key.data);
-          multisig_keys = m_wallet->decrypt(multisig_keys, key, true);
+          multisig_keys = m_wallet->decrypt<epee::wipeable_string>(std::string(multisig_keys.data(), multisig_keys.size()), key, true);
         }
         else
           m_recovery_key = cryptonote::decrypt_key(m_recovery_key, seed_pass);
@@ -3478,7 +3539,7 @@ boost::optional<epee::wipeable_string> simple_wallet::new_wallet(const boost::pr
   }
 
   // convert rng value to electrum-style word list
-  std::string electrum_words;
+  epee::wipeable_string electrum_words;
 
   crypto::ElectrumWords::bytes_to_words(recovery_val, electrum_words, mnemonic_language);
 
@@ -3586,7 +3647,7 @@ boost::optional<epee::wipeable_string> simple_wallet::new_wallet(const boost::pr
 }
 //----------------------------------------------------------------------------------------------------
 boost::optional<epee::wipeable_string> simple_wallet::new_wallet(const boost::program_options::variables_map& vm,
-    const std::string &multisig_keys, const std::string &old_language)
+    const epee::wipeable_string &multisig_keys, const std::string &old_language)
 {
   auto rc = tools::wallet2::make_new(vm, password_prompter);
   m_wallet = std::move(rc.first);
@@ -3697,7 +3758,7 @@ bool simple_wallet::open_wallet(const boost::program_options::variables_map& vm)
         m_wallet->rewrite(m_wallet_file, password);
 
         // Display the seed
-        std::string seed;
+        epee::wipeable_string seed;
         m_wallet->get_seed(seed);
         print_seed(seed);
       }
diff --git a/src/simplewallet/simplewallet.h b/src/simplewallet/simplewallet.h
index 472ad0c00..c8e17ea6e 100644
--- a/src/simplewallet/simplewallet.h
+++ b/src/simplewallet/simplewallet.h
@@ -44,6 +44,7 @@
 #include "cryptonote_basic/cryptonote_basic_impl.h"
 #include "wallet/wallet2.h"
 #include "console_handler.h"
+#include "wipeable_string.h"
 #include "common/i18n.h"
 #include "common/password.h"
 #include "crypto/crypto.h"  // for definition of crypto::secret_key
@@ -96,7 +97,7 @@ namespace cryptonote
     boost::optional<epee::wipeable_string> new_wallet(const boost::program_options::variables_map& vm, const cryptonote::account_public_address& address,
         const boost::optional<crypto::secret_key>& spendkey, const crypto::secret_key& viewkey);
     boost::optional<epee::wipeable_string> new_wallet(const boost::program_options::variables_map& vm,
-        const std::string &multisig_keys, const std::string &old_language);
+        const epee::wipeable_string &multisig_keys, const std::string &old_language);
     boost::optional<epee::wipeable_string> new_wallet(const boost::program_options::variables_map& vm, const std::string& device_name);
     bool open_wallet(const boost::program_options::variables_map& vm);
     bool close_wallet();
@@ -238,7 +239,7 @@ namespace cryptonote
      * \brief Prints the seed with a nice message
      * \param seed seed to print
      */
-    void print_seed(std::string seed);
+    void print_seed(const epee::wipeable_string &seed);
 
     /*!
      * \brief Gets the word seed language from the user.
@@ -329,7 +330,7 @@ namespace cryptonote
     std::string m_import_path;
     std::string m_subaddress_lookahead;
 
-    std::string m_electrum_seed;  // electrum-style seed parameter
+    epee::wipeable_string m_electrum_seed;  // electrum-style seed parameter
 
     crypto::secret_key m_recovery_key;  // recovery key (used as random for wallet gen)
     bool m_restore_deterministic_wallet;  // recover flag
diff --git a/src/wallet/api/wallet.cpp b/src/wallet/api/wallet.cpp
index b48bf07e0..e75bee5c9 100644
--- a/src/wallet/api/wallet.cpp
+++ b/src/wallet/api/wallet.cpp
@@ -733,10 +733,10 @@ bool WalletImpl::close(bool store)
 
 std::string WalletImpl::seed() const
 {
-    std::string seed;
+    epee::wipeable_string seed;
     if (m_wallet)
         m_wallet->get_seed(seed);
-    return seed;
+    return std::string(seed.data(), seed.size()); // TODO
 }
 
 std::string WalletImpl::getSeedLanguage() const
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 9deaad09b..e61e437c0 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -789,7 +789,7 @@ bool wallet2::is_deterministic() const
   return keys_deterministic;
 }
 //----------------------------------------------------------------------------------------------------
-bool wallet2::get_seed(std::string& electrum_words, const epee::wipeable_string &passphrase) const
+bool wallet2::get_seed(epee::wipeable_string& electrum_words, const epee::wipeable_string &passphrase) const
 {
   bool keys_deterministic = is_deterministic();
   if (!keys_deterministic)
@@ -815,7 +815,7 @@ bool wallet2::get_seed(std::string& electrum_words, const epee::wipeable_string
   return true;
 }
 //----------------------------------------------------------------------------------------------------
-bool wallet2::get_multisig_seed(std::string& seed, const epee::wipeable_string &passphrase, bool raw) const
+bool wallet2::get_multisig_seed(epee::wipeable_string& seed, const epee::wipeable_string &passphrase, bool raw) const
 {
   bool ready;
   uint32_t threshold, total;
@@ -838,7 +838,7 @@ bool wallet2::get_multisig_seed(std::string& seed, const epee::wipeable_string &
   crypto::secret_key skey;
   crypto::public_key pkey;
   const account_keys &keys = get_account().get_keys();
-  std::string data;
+  epee::wipeable_string data;
   data.append((const char*)&threshold, sizeof(uint32_t));
   data.append((const char*)&total, sizeof(uint32_t));
   skey = keys.m_spend_secret_key;
@@ -864,7 +864,7 @@ bool wallet2::get_multisig_seed(std::string& seed, const epee::wipeable_string &
 
   if (raw)
   {
-    seed = epee::string_tools::buff_to_hex_nodelimer(data);
+    seed = epee::to_hex::wipeable_string({(const unsigned char*)data.data(), data.size()});
   }
   else
   {
@@ -3161,7 +3161,7 @@ bool wallet2::verify_password(const std::string& keys_file_name, const epee::wip
  * \param  create_address_file  Whether to create an address file
  */
 void wallet2::generate(const std::string& wallet_, const epee::wipeable_string& password,
-  const std::string& multisig_data, bool create_address_file)
+  const epee::wipeable_string& multisig_data, bool create_address_file)
 {
   clear();
   prepare_file_names(wallet_);
@@ -10671,14 +10671,14 @@ size_t wallet2::import_multisig(std::vector<cryptonote::blobdata> blobs)
   return n_outputs;
 }
 //----------------------------------------------------------------------------------------------------
-std::string wallet2::encrypt(const std::string &plaintext, const crypto::secret_key &skey, bool authenticated) const
+std::string wallet2::encrypt(const char *plaintext, size_t len, const crypto::secret_key &skey, bool authenticated) const
 {
   crypto::chacha_key key;
   crypto::generate_chacha_key(&skey, sizeof(skey), key, m_kdf_rounds);
   std::string ciphertext;
   crypto::chacha_iv iv = crypto::rand<crypto::chacha_iv>();
-  ciphertext.resize(plaintext.size() + sizeof(iv) + (authenticated ? sizeof(crypto::signature) : 0));
-  crypto::chacha20(plaintext.data(), plaintext.size(), key, iv, &ciphertext[sizeof(iv)]);
+  ciphertext.resize(len + sizeof(iv) + (authenticated ? sizeof(crypto::signature) : 0));
+  crypto::chacha20(plaintext, len, key, iv, &ciphertext[sizeof(iv)]);
   memcpy(&ciphertext[0], &iv, sizeof(iv));
   if (authenticated)
   {
@@ -10692,12 +10692,28 @@ std::string wallet2::encrypt(const std::string &plaintext, const crypto::secret_
   return ciphertext;
 }
 //----------------------------------------------------------------------------------------------------
+std::string wallet2::encrypt(const epee::span<char> &plaintext, const crypto::secret_key &skey, bool authenticated) const
+{
+  return encrypt(plaintext.data(), plaintext.size(), skey, authenticated);
+}
+//----------------------------------------------------------------------------------------------------
+std::string wallet2::encrypt(const std::string &plaintext, const crypto::secret_key &skey, bool authenticated) const
+{
+  return encrypt(plaintext.data(), plaintext.size(), skey, authenticated);
+}
+//----------------------------------------------------------------------------------------------------
+std::string wallet2::encrypt(const epee::wipeable_string &plaintext, const crypto::secret_key &skey, bool authenticated) const
+{
+  return encrypt(plaintext.data(), plaintext.size(), skey, authenticated);
+}
+//----------------------------------------------------------------------------------------------------
 std::string wallet2::encrypt_with_view_secret_key(const std::string &plaintext, bool authenticated) const
 {
   return encrypt(plaintext, get_account().get_keys().m_view_secret_key, authenticated);
 }
 //----------------------------------------------------------------------------------------------------
-std::string wallet2::decrypt(const std::string &ciphertext, const crypto::secret_key &skey, bool authenticated) const
+template<typename T>
+T wallet2::decrypt(const std::string &ciphertext, const crypto::secret_key &skey, bool authenticated) const
 {
   const size_t prefix_size = sizeof(chacha_iv) + (authenticated ? sizeof(crypto::signature) : 0);
   THROW_WALLET_EXCEPTION_IF(ciphertext.size() < prefix_size,
@@ -10706,8 +10722,6 @@ std::string wallet2::decrypt(const std::string &ciphertext, const crypto::secret
   crypto::chacha_key key;
   crypto::generate_chacha_key(&skey, sizeof(skey), key, m_kdf_rounds);
   const crypto::chacha_iv &iv = *(const crypto::chacha_iv*)&ciphertext[0];
-  std::string plaintext;
-  plaintext.resize(ciphertext.size() - prefix_size);
   if (authenticated)
   {
     crypto::hash hash;
@@ -10718,10 +10732,14 @@ std::string wallet2::decrypt(const std::string &ciphertext, const crypto::secret
     THROW_WALLET_EXCEPTION_IF(!crypto::check_signature(hash, pkey, signature),
       error::wallet_internal_error, "Failed to authenticate ciphertext");
   }
-  crypto::chacha20(ciphertext.data() + sizeof(iv), ciphertext.size() - prefix_size, key, iv, &plaintext[0]);
-  return plaintext;
+  std::unique_ptr<char[]> buffer{new char[ciphertext.size() - prefix_size]};
+  auto wiper = epee::misc_utils::create_scope_leave_handler([&]() { memwipe(buffer.get(), ciphertext.size() - prefix_size); });
+  crypto::chacha20(ciphertext.data() + sizeof(iv), ciphertext.size() - prefix_size, key, iv, buffer.get());
+  return T(buffer.get(), ciphertext.size() - prefix_size);
 }
 //----------------------------------------------------------------------------------------------------
+template epee::wipeable_string wallet2::decrypt(const std::string &ciphertext, const crypto::secret_key &skey, bool authenticated) const;
+//----------------------------------------------------------------------------------------------------
 std::string wallet2::decrypt_with_view_secret_key(const std::string &ciphertext, bool authenticated) const
 {
   return decrypt(ciphertext, get_account().get_keys().m_view_secret_key, authenticated);
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index d04156461..86fee0da7 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -495,7 +495,7 @@ namespace tools
      * \param  create_address_file  Whether to create an address file
      */
     void generate(const std::string& wallet_, const epee::wipeable_string& password,
-      const std::string& multisig_data, bool create_address_file = false);
+      const epee::wipeable_string& multisig_data, bool create_address_file = false);
 
     /*!
      * \brief Generates a wallet or restores one.
@@ -637,7 +637,7 @@ namespace tools
      * \brief Checks if deterministic wallet
      */
     bool is_deterministic() const;
-    bool get_seed(std::string& electrum_words, const epee::wipeable_string &passphrase = epee::wipeable_string()) const;
+    bool get_seed(epee::wipeable_string& electrum_words, const epee::wipeable_string &passphrase = epee::wipeable_string()) const;
 
     /*!
     * \brief Checks if light wallet. A light wallet sends view key to a server where the blockchain is scanned.
@@ -691,7 +691,7 @@ namespace tools
     bool multisig(bool *ready = NULL, uint32_t *threshold = NULL, uint32_t *total = NULL) const;
     bool has_multisig_partial_key_images() const;
     bool has_unknown_key_images() const;
-    bool get_multisig_seed(std::string& seed, const epee::wipeable_string &passphrase = std::string(), bool raw = true) const;
+    bool get_multisig_seed(epee::wipeable_string& seed, const epee::wipeable_string &passphrase = std::string(), bool raw = true) const;
     bool key_on_device() const { return m_key_on_device; }
 
     // locked & unlocked balance of given or current subaddress account
@@ -1054,9 +1054,12 @@ namespace tools
     void update_pool_state(bool refreshed = false);
     void remove_obsolete_pool_txs(const std::vector<crypto::hash> &tx_hashes);
 
+    std::string encrypt(const char *plaintext, size_t len, const crypto::secret_key &skey, bool authenticated = true) const;
+    std::string encrypt(const epee::span<char> &span, const crypto::secret_key &skey, bool authenticated = true) const;
     std::string encrypt(const std::string &plaintext, const crypto::secret_key &skey, bool authenticated = true) const;
+    std::string encrypt(const epee::wipeable_string &plaintext, const crypto::secret_key &skey, bool authenticated = true) const;
     std::string encrypt_with_view_secret_key(const std::string &plaintext, bool authenticated = true) const;
-    std::string decrypt(const std::string &ciphertext, const crypto::secret_key &skey, bool authenticated = true) const;
+    template<typename T=std::string> T decrypt(const std::string &ciphertext, const crypto::secret_key &skey, bool authenticated = true) const;
     std::string decrypt_with_view_secret_key(const std::string &ciphertext, bool authenticated = true) const;
 
     std::string make_uri(const std::string &address, const std::string &payment_id, uint64_t amount, const std::string &tx_description, const std::string &recipient_name, std::string &error) const;
diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
index 510cb3e58..136cd0e2d 100644
--- a/src/wallet/wallet_rpc_server.cpp
+++ b/src/wallet/wallet_rpc_server.cpp
@@ -1574,11 +1574,13 @@ namespace tools
 
       if (req.key_type.compare("mnemonic") == 0)
       {
-        if (!m_wallet->get_seed(res.key))
+        epee::wipeable_string seed;
+        if (!m_wallet->get_seed(seed))
         {
             er.message = "The wallet is non-deterministic. Cannot display seed.";
             return false;
         }
+        res.key = std::string(seed.data(), seed.size()); // send to the network, then wipe RAM :D
       }
       else if(req.key_type.compare("view_key") == 0)
       {
diff --git a/tests/unit_tests/CMakeLists.txt b/tests/unit_tests/CMakeLists.txt
index 3c7414640..f47192ea9 100644
--- a/tests/unit_tests/CMakeLists.txt
+++ b/tests/unit_tests/CMakeLists.txt
@@ -72,7 +72,8 @@ set(unit_tests_sources
   ringct.cpp
   output_selection.cpp
   vercmp.cpp
-  ringdb.cpp)
+  ringdb.cpp
+  wipeable_string.cpp)
 
 set(unit_tests_headers
   unit_tests_utils.h)
diff --git a/tests/unit_tests/mnemonics.cpp b/tests/unit_tests/mnemonics.cpp
index 8fa3192b9..0b74a6b94 100644
--- a/tests/unit_tests/mnemonics.cpp
+++ b/tests/unit_tests/mnemonics.cpp
@@ -27,6 +27,8 @@
 // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "gtest/gtest.h"
+#include "wipeable_string.h"
+#include "mnemonics/language_base.h"
 #include "mnemonics/electrum-words.h"
 #include "crypto/crypto.h"
 #include <stdlib.h>
@@ -74,14 +76,16 @@ namespace
   void test_language(const Language::Base &language)
   {
     const std::vector<std::string> &word_list = language.get_word_list();
-    std::string seed = "", return_seed = "";
+    epee::wipeable_string w_seed = "", w_return_seed = "";
+    std::string seed, return_seed;
     // Generate a random seed without checksum
     crypto::secret_key randkey;
     for (size_t ii = 0; ii < sizeof(randkey); ++ii)
     {
       randkey.data[ii] = rand();
     }
-    crypto::ElectrumWords::bytes_to_words(randkey, seed, language.get_language_name());
+    crypto::ElectrumWords::bytes_to_words(randkey, w_seed, language.get_language_name());
+    seed = std::string(w_seed.data(), w_seed.size());
     // remove the checksum word
     const char *space = strrchr(seed.c_str(), ' ');
     ASSERT_TRUE(space != NULL);
@@ -103,7 +107,8 @@ namespace
     ASSERT_STREQ(language.get_language_name().c_str(), language_name.c_str());
 
     // Convert the secret key back to seed
-    crypto::ElectrumWords::bytes_to_words(key, return_seed, language.get_language_name());
+    crypto::ElectrumWords::bytes_to_words(key, w_return_seed, language.get_language_name());
+    return_seed = std::string(w_return_seed.data(), w_return_seed.size());
     ASSERT_EQ(true, res);
     std::cout << "Returned seed:\n";
     std::cout << return_seed << std::endl;
@@ -126,8 +131,9 @@ namespace
     std::cout << "Detected language: " << language_name << std::endl;
     ASSERT_STREQ(language.get_language_name().c_str(), language_name.c_str());
 
-    return_seed = "";
-    crypto::ElectrumWords::bytes_to_words(key, return_seed, language.get_language_name());
+    w_return_seed = "";
+    crypto::ElectrumWords::bytes_to_words(key, w_return_seed, language.get_language_name());
+    return_seed = std::string(w_return_seed.data(), w_return_seed.size());
     ASSERT_EQ(true, res);
     std::cout << "Returned seed:\n";
     std::cout << return_seed << std::endl;
@@ -202,3 +208,17 @@ TEST(mnemonics, language_detection_with_bad_checksum)
     ASSERT_EQ(true, res);
     ASSERT_STREQ(language_name.c_str(), "Português");
 }
+
+TEST(mnemonics, utf8prefix)
+{
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("foo"), 0) == "");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("foo"), 1) == "f");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("foo"), 2) == "fo");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("foo"), 3) == "foo");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("foo"), 4) == "foo");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("æon"), 0) == "");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("æon"), 1) == "æ");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("æon"), 2) == "æo");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("æon"), 3) == "æon");
+  ASSERT_TRUE(Language::utf8prefix(epee::wipeable_string("æon"), 4) == "æon");
+}
diff --git a/tests/unit_tests/wipeable_string.cpp b/tests/unit_tests/wipeable_string.cpp
new file mode 100644
index 000000000..5ea1c1729
--- /dev/null
+++ b/tests/unit_tests/wipeable_string.cpp
@@ -0,0 +1,204 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <boost/optional/optional.hpp>
+#include <string.h>
+#include "gtest/gtest.h"
+
+#include "misc_log_ex.h"
+#include "wipeable_string.h"
+
+TEST(wipeable_string, ctor)
+{
+  epee::wipeable_string s0;
+  ASSERT_EQ(s0.size(), 0);
+
+  epee::wipeable_string s1(std::string("foo"));
+  ASSERT_EQ(s1.size(), 3);
+  ASSERT_TRUE(!memcmp(s1.data(), "foo", s1.size()));
+
+  epee::wipeable_string s2(std::string("bar"));
+  ASSERT_EQ(s2.size(), 3);
+  ASSERT_TRUE(!memcmp(s2.data(), "bar", s2.size()));
+
+  epee::wipeable_string s3(std::string("quux"));
+  ASSERT_EQ(s3.size(), 4);
+  ASSERT_TRUE(!memcmp(s3.data(), "quux", s3.size()));
+}
+
+TEST(wipeable_string, wipe)
+{
+  epee::wipeable_string s0(std::string("foo"));
+  ASSERT_EQ(s0.size(), 3);
+  s0.wipe();
+  ASSERT_EQ(s0.size(), 3);
+  ASSERT_TRUE(!memcmp(s0.data(), "\0\0\0", 3));
+}
+
+TEST(wipeable_string, clear)
+{
+  epee::wipeable_string s0(std::string("foo"));
+  ASSERT_EQ(s0.size(), 3);
+  s0.clear();
+  ASSERT_EQ(s0.size(), 0);
+}
+
+TEST(wipeable_string, push_back)
+{
+  epee::wipeable_string s0(std::string("fo"));
+  ASSERT_EQ(s0.size(), 2);
+  s0.push_back('o');
+  ASSERT_EQ(s0.size(), 3);
+  ASSERT_TRUE(!memcmp(s0.data(), "foo", s0.size()));
+}
+
+TEST(wipeable_string, append_char)
+{
+  epee::wipeable_string s0(std::string("fo"));
+  ASSERT_EQ(s0.size(), 2);
+  s0 += 'o';
+  ASSERT_EQ(s0.size(), 3);
+  ASSERT_TRUE(!memcmp(s0.data(), "foo", s0.size()));
+}
+
+TEST(wipeable_string, append_string)
+{
+  epee::wipeable_string s0(std::string("foo"));
+  ASSERT_EQ(s0.size(), 3);
+  s0 += "bar";
+  ASSERT_EQ(s0.size(), 6);
+  ASSERT_TRUE(!memcmp(s0.data(), "foobar", s0.size()));
+}
+
+TEST(wipeable_string, empty)
+{
+  epee::wipeable_string s0;
+  ASSERT_TRUE(s0.empty());
+  s0.push_back(' ');
+  ASSERT_FALSE(s0.empty());
+  ASSERT_EQ(s0.pop_back(), ' ');
+  ASSERT_TRUE(s0.empty());
+}
+
+TEST(wipeable_string, pop_back)
+{
+  epee::wipeable_string s = "test";
+  ASSERT_EQ(s.size(), 4);
+  ASSERT_EQ(s.pop_back(), 't');
+  ASSERT_EQ(s.size(), 3);
+  ASSERT_TRUE(!memcmp(s.data(), "tes", s.size()));
+}
+
+TEST(wipeable_string, equal)
+{
+  epee::wipeable_string s0 = "foo";
+  epee::wipeable_string s1 = "bar";
+  epee::wipeable_string s0_2 = "foo";
+  ASSERT_TRUE(s0 == s0);
+  ASSERT_TRUE(s0 == s0_2);
+  ASSERT_TRUE(s1 == s1);
+  ASSERT_FALSE(s1 == s0);
+  ASSERT_FALSE(s1 == s0_2);
+}
+
+TEST(wipeable_string, not_equal)
+{
+  epee::wipeable_string s0 = "foo";
+  epee::wipeable_string s1 = "bar";
+  epee::wipeable_string s0_2 = "foo";
+  ASSERT_FALSE(s0 != s0);
+  ASSERT_FALSE(s0 != s0_2);
+  ASSERT_FALSE(s1 != s1);
+  ASSERT_TRUE(s1 != s0);
+  ASSERT_TRUE(s1 != s0_2);
+}
+
+static epee::wipeable_string trimmed(const char *s)
+{
+  epee::wipeable_string str(s);
+  str.trim();
+  return str;
+}
+
+TEST(wipeable_string, trim)
+{
+  ASSERT_TRUE(trimmed("") == "");
+  ASSERT_TRUE(trimmed(" ") == "");
+  ASSERT_TRUE(trimmed("  ") == "");
+  ASSERT_TRUE(trimmed("a") == "a");
+  ASSERT_TRUE(trimmed(" a") == "a");
+  ASSERT_TRUE(trimmed("  a") == "a");
+  ASSERT_TRUE(trimmed("a ") == "a");
+  ASSERT_TRUE(trimmed("a  ") == "a");
+  ASSERT_TRUE(trimmed(" a  ") == "a");
+  ASSERT_TRUE(trimmed("  a  ") == "a");
+  ASSERT_TRUE(trimmed("  ab  ") == "ab");
+  ASSERT_TRUE(trimmed("  a b  ") == "a b");
+  ASSERT_TRUE(trimmed("  a  b  ") == "a  b");
+}
+
+static bool check_split(const char *s, const std::vector<epee::wipeable_string> &v)
+{
+  epee::wipeable_string str(s);
+  std::vector<epee::wipeable_string> fields;
+  str.split(fields);
+  return v == fields;
+}
+
+TEST(wipeable_string, split)
+{
+  ASSERT_TRUE(check_split("", {}));
+  ASSERT_TRUE(check_split("foo", {"foo"}));
+  ASSERT_TRUE(check_split("  foo   ", {"foo"}));
+  ASSERT_TRUE(check_split("foo bar", {"foo", "bar"}));
+  ASSERT_TRUE(check_split("foo     bar", {"foo", "bar"}));
+  ASSERT_TRUE(check_split("foo     bar   baz", {"foo", "bar", "baz"}));
+  ASSERT_TRUE(check_split(" foo     bar   baz         ", {"foo", "bar", "baz"}));
+  ASSERT_TRUE(check_split("  foo     bar   baz", {"foo", "bar", "baz"}));
+  ASSERT_TRUE(check_split("foo     bar   baz ", {"foo", "bar", "baz"}));
+}
+
+TEST(wipeable_string, parse_hexstr)
+{
+  boost::optional<epee::wipeable_string> s;
+
+  ASSERT_EQ(boost::none, epee::wipeable_string("x").parse_hexstr());
+  ASSERT_EQ(boost::none, epee::wipeable_string("x0000000000000000").parse_hexstr());
+  ASSERT_EQ(boost::none, epee::wipeable_string("0000000000000000x").parse_hexstr());
+  ASSERT_EQ(boost::none, epee::wipeable_string("0").parse_hexstr());
+  ASSERT_EQ(boost::none, epee::wipeable_string("000").parse_hexstr());
+
+  ASSERT_TRUE((s = epee::wipeable_string("").parse_hexstr()));
+  ASSERT_EQ(*s, "");
+  ASSERT_TRUE((s = epee::wipeable_string("00").parse_hexstr()));
+  ASSERT_EQ(*s, epee::wipeable_string("", 1));
+  ASSERT_TRUE((s = epee::wipeable_string("41").parse_hexstr()));
+  ASSERT_EQ(*s, epee::wipeable_string("A"));
+  ASSERT_TRUE((s = epee::wipeable_string("414243").parse_hexstr()));
+  ASSERT_EQ(*s, epee::wipeable_string("ABC"));
+}