diff --git a/CMakeLists.txt b/CMakeLists.txt
index fbd7f4212..d8407dbda 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -328,6 +328,7 @@ set(TL_DOTNET_SCHEME_SOURCE
 set(TDLIB_SOURCE
   td/mtproto/AuthData.cpp
   td/mtproto/crypto.cpp
+  td/mtproto/DhHandshake.cpp
   td/mtproto/Handshake.cpp
   td/mtproto/HandshakeActor.cpp
   td/mtproto/HttpTransport.cpp
@@ -441,6 +442,7 @@ set(TDLIB_SOURCE
   td/mtproto/AuthKey.h
   td/mtproto/crypto.h
   td/mtproto/CryptoStorer.h
+  td/mtproto/DhHandshake.h
   td/mtproto/Handshake.h
   td/mtproto/HandshakeActor.h
   td/mtproto/HandshakeConnection.h
diff --git a/benchmark/bench_handshake.cpp b/benchmark/bench_handshake.cpp
index f59afe608..05f3185ff 100644
--- a/benchmark/bench_handshake.cpp
+++ b/benchmark/bench_handshake.cpp
@@ -6,7 +6,7 @@
 //
 #include "td/utils/benchmark.h"  // for bench, do_not_optimize_away, etc
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/utils/base64.h"
 #include "td/utils/logging.h"
diff --git a/td/mtproto/DhHandshake.cpp b/td/mtproto/DhHandshake.cpp
new file mode 100644
index 000000000..f9f7240b8
--- /dev/null
+++ b/td/mtproto/DhHandshake.cpp
@@ -0,0 +1,231 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#include "td/mtproto/DhHandshake.h"
+
+#include "td/utils/as.h"
+#include "td/utils/crypto.h"
+#include "td/utils/logging.h"
+#include "td/utils/misc.h"
+#include "td/utils/Random.h"
+#include "td/utils/Slice.h"
+#include "td/utils/Status.h"
+
+#include <cstring>
+
+namespace td {
+
+Status DhHandshake::check_config(Slice prime_str, const BigNum &prime, int32 g_int, BigNumContext &ctx,
+                                 DhCallback *callback) {
+  // check that 2^2047 <= p < 2^2048
+  if (prime.get_num_bits() != 2048) {
+    return Status::Error("p is not 2048-bit number");
+  }
+
+  // g generates a cyclic subgroup of prime order (p - 1) / 2, i.e. is a quadratic residue mod p.
+  // Since g is always equal to 2, 3, 4, 5, 6 or 7, this is easily done using quadratic reciprocity law,
+  // yielding a simple condition on
+  // * p mod 4g - namely, p mod 8 = 7 for g = 2; p mod 3 = 2 for g = 3;
+  // * no extra condition for g = 4;
+  // * p mod 5 = 1 or 4 for g = 5;
+  // * p mod 24 = 19 or 23 for g = 6;
+  // * p mod 7 = 3, 5 or 6 for g = 7.
+
+  bool mod_ok;
+  uint32 mod_r;
+  switch (g_int) {
+    case 2:
+      mod_ok = prime % 8 == 7u;
+      break;
+    case 3:
+      mod_ok = prime % 3 == 2u;
+      break;
+    case 4:
+      mod_ok = true;
+      break;
+    case 5:
+      mod_ok = (mod_r = prime % 5) == 1u || mod_r == 4u;
+      break;
+    case 6:
+      mod_ok = (mod_r = prime % 24) == 19u || mod_r == 23u;
+      break;
+    case 7:
+      mod_ok = (mod_r = prime % 7) == 3u || mod_r == 5u || mod_r == 6u;
+      break;
+    default:
+      mod_ok = false;
+  }
+  if (!mod_ok) {
+    return Status::Error("Bad prime mod 4g");
+  }
+
+  // check whether p is a safe prime (meaning that both p and (p - 1) / 2 are prime)
+  int is_good_prime = -1;
+  if (callback) {
+    is_good_prime = callback->is_good_prime(prime_str);
+  }
+  if (is_good_prime != -1) {
+    return is_good_prime ? Status::OK() : Status::Error("p or (p - 1) / 2 is not a prime number");
+  }
+  if (!prime.is_prime(ctx)) {
+    if (callback) {
+      callback->add_bad_prime(prime_str);
+    }
+    return Status::Error("p is not a prime number");
+  }
+
+  BigNum half_prime = prime;
+  half_prime -= 1;
+  half_prime /= 2;
+  if (!half_prime.is_prime(ctx)) {
+    if (callback) {
+      callback->add_bad_prime(prime_str);
+    }
+    return Status::Error("(p - 1) / 2 is not a prime number");
+  }
+  if (callback) {
+    callback->add_good_prime(prime_str);
+  }
+  return Status::OK();
+}
+
+Status DhHandshake::dh_check(const BigNum &prime, const BigNum &g_a, const BigNum &g_b) {
+  // IMPORTANT: Apart from the conditions on the Diffie-Hellman prime dh_prime and generator g, both sides are
+  // to check that g, g_a and g_b are greater than 1 and less than dh_prime - 1.
+  // We recommend checking that g_a and g_b are between 2^{2048-64} and dh_prime - 2^{2048-64} as well.
+
+  CHECK(prime.get_num_bits() == 2048);
+  BigNum left;
+  left.set_value(0);
+  left.set_bit(2048 - 64);
+
+  BigNum right;
+  BigNum::sub(right, prime, left);
+
+  if (BigNum::compare(left, g_a) > 0 || BigNum::compare(g_a, right) > 0 || BigNum::compare(left, g_b) > 0 ||
+      BigNum::compare(g_b, right) > 0) {
+    std::string x(2048, '0');
+    std::string y(2048, '0');
+    for (int i = 0; i < 2048; i++) {
+      if (g_a.is_bit_set(i)) {
+        x[i] = '1';
+      }
+      if (g_b.is_bit_set(i)) {
+        y[i] = '1';
+      }
+    }
+    LOG(ERROR) << x;
+    LOG(ERROR) << y;
+    return Status::Error("g^a or g^b is not between 2^{2048-64} and dh_prime - 2^{2048-64}");
+  }
+
+  return Status::OK();
+}
+
+void DhHandshake::set_config(int32 g_int, Slice prime_str) {
+  has_config_ = true;
+  prime_ = BigNum::from_binary(prime_str);
+  prime_str_ = prime_str.str();
+
+  b_ = BigNum();
+  g_b_ = BigNum();
+
+  BigNum::random(b_, 2048, -1, 0);
+
+  // g^b
+  g_int_ = g_int;
+  g_.set_value(g_int_);
+
+  BigNum::mod_exp(g_b_, g_, b_, prime_, ctx_);
+}
+
+Status DhHandshake::check_config(int32 g_int, Slice prime_str, DhCallback *callback) {
+  BigNumContext ctx;
+  auto prime = BigNum::from_binary(prime_str);
+  return check_config(prime_str, prime, g_int, ctx, callback);
+}
+
+void DhHandshake::set_g_a_hash(Slice g_a_hash) {
+  has_g_a_hash_ = true;
+  ok_g_a_hash_ = false;
+  CHECK(!has_g_a_);
+  g_a_hash_ = g_a_hash.str();
+}
+
+void DhHandshake::set_g_a(Slice g_a_str) {
+  has_g_a_ = true;
+  if (has_g_a_hash_) {
+    string g_a_hash(32, ' ');
+    sha256(g_a_str, g_a_hash);
+    ok_g_a_hash_ = g_a_hash == g_a_hash_;
+  }
+  g_a_ = BigNum::from_binary(g_a_str);
+}
+
+string DhHandshake::get_g_a() const {
+  CHECK(has_g_a_);
+  return g_a_.to_binary();
+}
+
+string DhHandshake::get_g_b() const {
+  CHECK(has_config_);
+  return g_b_.to_binary();
+}
+string DhHandshake::get_g_b_hash() const {
+  string g_b_hash(32, ' ');
+  sha256(get_g_b(), g_b_hash);
+  return g_b_hash;
+}
+
+Status DhHandshake::run_checks(bool skip_config_check, DhCallback *callback) {
+  CHECK(has_g_a_ && has_config_);
+
+  if (has_g_a_hash_ && !ok_g_a_hash_) {
+    return Status::Error("g_a_hash mismatch");
+  }
+
+  if (!skip_config_check) {
+    TRY_STATUS(check_config(prime_str_, prime_, g_int_, ctx_, callback));
+  }
+
+  return dh_check(prime_, g_a_, g_b_);
+}
+
+BigNum DhHandshake::get_g() const {
+  CHECK(has_config_);
+  return g_;
+}
+
+BigNum DhHandshake::get_p() const {
+  CHECK(has_config_);
+  return prime_;
+}
+
+BigNum DhHandshake::get_b() const {
+  CHECK(has_config_);
+  return b_;
+}
+
+BigNum DhHandshake::get_g_ab() {
+  CHECK(has_g_a_ && has_config_);
+  BigNum g_ab;
+  BigNum::mod_exp(g_ab, g_a_, b_, prime_, ctx_);
+  return g_ab;
+}
+
+std::pair<int64, string> DhHandshake::gen_key() {
+  string key = get_g_ab().to_binary(2048 / 8);
+  auto key_id = calc_key_id(key);
+  return std::pair<int64, string>(key_id, std::move(key));
+}
+
+int64 DhHandshake::calc_key_id(Slice auth_key) {
+  UInt<160> auth_key_sha1;
+  sha1(auth_key, auth_key_sha1.raw);
+  return as<int64>(auth_key_sha1.raw + 12);
+}
+
+}  // namespace td
diff --git a/td/mtproto/DhHandshake.h b/td/mtproto/DhHandshake.h
new file mode 100644
index 000000000..e360f5b12
--- /dev/null
+++ b/td/mtproto/DhHandshake.h
@@ -0,0 +1,135 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#pragma once
+
+#include "td/utils/BigNum.h"
+#include "td/utils/common.h"
+#include "td/utils/Slice.h"
+#include "td/utils/Status.h"
+
+#include <utility>
+
+namespace td {
+
+/*** DH ***/
+class DhCallback {
+ public:
+  DhCallback() = default;
+  DhCallback(const DhCallback &) = delete;
+  DhCallback &operator=(const DhCallback &) = delete;
+  DhCallback(DhCallback &&) = delete;
+  DhCallback &operator=(DhCallback &&) = delete;
+  virtual ~DhCallback() = default;
+
+  virtual int is_good_prime(Slice prime_str) const = 0;
+  virtual void add_good_prime(Slice prime_str) const = 0;
+  virtual void add_bad_prime(Slice prime_str) const = 0;
+};
+
+class DhHandshake {
+ public:
+  void set_config(int32 g_int, Slice prime_str);
+
+  static Status check_config(int32 g_int, Slice prime_str, DhCallback *callback);
+
+  bool has_config() const {
+    return has_config_;
+  }
+  void set_g_a_hash(Slice g_a_hash);
+  void set_g_a(Slice g_a_str);
+  bool has_g_a() const {
+    return has_g_a_;
+  }
+  string get_g_a() const;
+  string get_g_b() const;
+  string get_g_b_hash() const;
+  Status run_checks(bool skip_config_check, DhCallback *callback) TD_WARN_UNUSED_RESULT;
+
+  BigNum get_g() const;
+  BigNum get_p() const;
+  BigNum get_b() const;
+  BigNum get_g_ab();
+
+  std::pair<int64, string> gen_key();
+
+  static int64 calc_key_id(Slice auth_key);
+
+  enum Flags { HasConfig = 1, HasGA = 2 };
+
+  template <class StorerT>
+  void store(StorerT &storer) const {
+    auto flags = 0;
+    if (has_config_) {
+      flags |= HasConfig;
+    }
+    if (has_g_a_) {
+      flags |= HasGA;
+    }
+    storer.store_int(flags);
+
+    if (has_config_) {
+      // prime_, prime_str_, b_, g_, g_int_, g_b_
+      storer.store_string(prime_str_);
+      storer.store_string(b_.to_binary());
+      storer.store_int(g_int_);
+      storer.store_string(g_b_.to_binary());
+    }
+    if (has_g_a_) {
+      storer.store_string(g_a_.to_binary());
+    }
+  }
+  template <class ParserT>
+  void parse(ParserT &parser) {
+    auto flags = parser.fetch_int();
+    if (flags & HasConfig) {
+      has_config_ = true;
+    }
+    if (flags & HasGA) {
+      has_g_a_ = true;
+    }
+    if (has_config_) {
+      // prime_, prime_str_, b_, g_, g_int_, g_b_
+      prime_str_ = parser.template fetch_string<std::string>();
+      prime_ = BigNum::from_binary(prime_str_);
+
+      b_ = BigNum::from_binary(parser.template fetch_string<string>());
+
+      g_int_ = parser.fetch_int();
+      g_.set_value(g_int_);
+
+      g_b_ = BigNum::from_binary(parser.template fetch_string<string>());
+    }
+    if (has_g_a_) {
+      g_a_ = BigNum::from_binary(parser.template fetch_string<string>());
+    }
+  }
+
+ private:
+  static Status check_config(Slice prime_str, const BigNum &prime, int32 g_int, BigNumContext &ctx,
+                             DhCallback *callback) TD_WARN_UNUSED_RESULT;
+
+  static Status dh_check(const BigNum &prime, const BigNum &g_a, const BigNum &g_b) TD_WARN_UNUSED_RESULT;
+
+  string prime_str_;
+  BigNum prime_;
+  BigNum g_;
+  int32 g_int_;
+  BigNum b_;
+  BigNum g_b_;
+  BigNum g_a_;
+
+  string g_a_hash_;
+  bool has_g_a_hash_{false};
+  bool ok_g_a_hash_{false};
+
+  bool has_config_ = false;
+  bool has_g_a_ = false;
+
+  BigNumContext ctx_;
+};
+
+}  // namespace td
diff --git a/td/mtproto/Handshake.cpp b/td/mtproto/Handshake.cpp
index d693cbe6f..6afa277a5 100644
--- a/td/mtproto/Handshake.cpp
+++ b/td/mtproto/Handshake.cpp
@@ -6,6 +6,7 @@
 //
 #include "td/mtproto/Handshake.h"
 
+#include "td/mtproto/crypto.h"
 #include "td/mtproto/utils.h"
 
 #include "td/mtproto/mtproto_api.h"
diff --git a/td/mtproto/Handshake.h b/td/mtproto/Handshake.h
index a71ea3ef9..7c28a514d 100644
--- a/td/mtproto/Handshake.h
+++ b/td/mtproto/Handshake.h
@@ -8,6 +8,7 @@
 
 #include "td/mtproto/AuthKey.h"
 #include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/utils/buffer.h"
 #include "td/utils/Slice.h"
diff --git a/td/mtproto/HandshakeConnection.h b/td/mtproto/HandshakeConnection.h
index 53aae3ee3..f9e9f44e8 100644
--- a/td/mtproto/HandshakeConnection.h
+++ b/td/mtproto/HandshakeConnection.h
@@ -12,8 +12,6 @@
 #include "td/mtproto/PacketInfo.h"
 #include "td/mtproto/PacketStorer.h"
 #include "td/mtproto/RawConnection.h"
-#include "td/mtproto/Transport.h"
-#include "td/mtproto/utils.h"
 
 #include "td/utils/buffer.h"
 #include "td/utils/common.h"
diff --git a/td/mtproto/SessionConnection.cpp b/td/mtproto/SessionConnection.cpp
index db0fb6be1..b7e8e8ecc 100644
--- a/td/mtproto/SessionConnection.cpp
+++ b/td/mtproto/SessionConnection.cpp
@@ -10,6 +10,7 @@
 #include "td/mtproto/CryptoStorer.h"
 #include "td/mtproto/PacketStorer.h"
 #include "td/mtproto/Transport.h"
+#include "td/mtproto/utils.h"
 
 #include "td/utils/as.h"
 #include "td/utils/format.h"
diff --git a/td/mtproto/SessionConnection.h b/td/mtproto/SessionConnection.h
index 5a3173523..ad7ad2839 100644
--- a/td/mtproto/SessionConnection.h
+++ b/td/mtproto/SessionConnection.h
@@ -6,9 +6,9 @@
 //
 #pragma once
 
-#include "td/mtproto/RawConnection.h"
 #include "td/mtproto/PacketInfo.h"
 #include "td/mtproto/Query.h"
+#include "td/mtproto/RawConnection.h"
 
 #include "td/utils/buffer.h"
 #include "td/utils/format.h"
diff --git a/td/mtproto/TcpTransport.h b/td/mtproto/TcpTransport.h
index 440483275..b1e0b6bfc 100644
--- a/td/mtproto/TcpTransport.h
+++ b/td/mtproto/TcpTransport.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "td/mtproto/IStreamTransport.h"
+#include "td/mtproto/TransportType.h"
 
 #include "td/utils/AesCtrByteFlow.h"
 #include "td/utils/buffer.h"
diff --git a/td/mtproto/crypto.cpp b/td/mtproto/crypto.cpp
index 167885849..e02f43e58 100644
--- a/td/mtproto/crypto.cpp
+++ b/td/mtproto/crypto.cpp
@@ -130,216 +130,6 @@ void RSA::decrypt(Slice from, MutableSlice to) const {
   std::memcpy(to.data(), result.c_str(), 256);
 }
 
-Status DhHandshake::check_config(Slice prime_str, const BigNum &prime, int32 g_int, BigNumContext &ctx,
-                                 DhCallback *callback) {
-  // check that 2^2047 <= p < 2^2048
-  if (prime.get_num_bits() != 2048) {
-    return Status::Error("p is not 2048-bit number");
-  }
-
-  // g generates a cyclic subgroup of prime order (p - 1) / 2, i.e. is a quadratic residue mod p.
-  // Since g is always equal to 2, 3, 4, 5, 6 or 7, this is easily done using quadratic reciprocity law,
-  // yielding a simple condition on
-  // * p mod 4g - namely, p mod 8 = 7 for g = 2; p mod 3 = 2 for g = 3;
-  // * no extra condition for g = 4;
-  // * p mod 5 = 1 or 4 for g = 5;
-  // * p mod 24 = 19 or 23 for g = 6;
-  // * p mod 7 = 3, 5 or 6 for g = 7.
-
-  bool mod_ok;
-  uint32 mod_r;
-  switch (g_int) {
-    case 2:
-      mod_ok = prime % 8 == 7u;
-      break;
-    case 3:
-      mod_ok = prime % 3 == 2u;
-      break;
-    case 4:
-      mod_ok = true;
-      break;
-    case 5:
-      mod_ok = (mod_r = prime % 5) == 1u || mod_r == 4u;
-      break;
-    case 6:
-      mod_ok = (mod_r = prime % 24) == 19u || mod_r == 23u;
-      break;
-    case 7:
-      mod_ok = (mod_r = prime % 7) == 3u || mod_r == 5u || mod_r == 6u;
-      break;
-    default:
-      mod_ok = false;
-  }
-  if (!mod_ok) {
-    return Status::Error("Bad prime mod 4g");
-  }
-
-  // check whether p is a safe prime (meaning that both p and (p - 1) / 2 are prime)
-  int is_good_prime = -1;
-  if (callback) {
-    is_good_prime = callback->is_good_prime(prime_str);
-  }
-  if (is_good_prime != -1) {
-    return is_good_prime ? Status::OK() : Status::Error("p or (p - 1) / 2 is not a prime number");
-  }
-  if (!prime.is_prime(ctx)) {
-    if (callback) {
-      callback->add_bad_prime(prime_str);
-    }
-    return Status::Error("p is not a prime number");
-  }
-
-  BigNum half_prime = prime;
-  half_prime -= 1;
-  half_prime /= 2;
-  if (!half_prime.is_prime(ctx)) {
-    if (callback) {
-      callback->add_bad_prime(prime_str);
-    }
-    return Status::Error("(p - 1) / 2 is not a prime number");
-  }
-  if (callback) {
-    callback->add_good_prime(prime_str);
-  }
-  return Status::OK();
-}
-
-Status DhHandshake::dh_check(const BigNum &prime, const BigNum &g_a, const BigNum &g_b) {
-  // IMPORTANT: Apart from the conditions on the Diffie-Hellman prime dh_prime and generator g, both sides are
-  // to check that g, g_a and g_b are greater than 1 and less than dh_prime - 1.
-  // We recommend checking that g_a and g_b are between 2^{2048-64} and dh_prime - 2^{2048-64} as well.
-
-  CHECK(prime.get_num_bits() == 2048);
-  BigNum left;
-  left.set_value(0);
-  left.set_bit(2048 - 64);
-
-  BigNum right;
-  BigNum::sub(right, prime, left);
-
-  if (BigNum::compare(left, g_a) > 0 || BigNum::compare(g_a, right) > 0 || BigNum::compare(left, g_b) > 0 ||
-      BigNum::compare(g_b, right) > 0) {
-    std::string x(2048, '0');
-    std::string y(2048, '0');
-    for (int i = 0; i < 2048; i++) {
-      if (g_a.is_bit_set(i)) {
-        x[i] = '1';
-      }
-      if (g_b.is_bit_set(i)) {
-        y[i] = '1';
-      }
-    }
-    LOG(ERROR) << x;
-    LOG(ERROR) << y;
-    return Status::Error("g^a or g^b is not between 2^{2048-64} and dh_prime - 2^{2048-64}");
-  }
-
-  return Status::OK();
-}
-
-void DhHandshake::set_config(int32 g_int, Slice prime_str) {
-  has_config_ = true;
-  prime_ = BigNum::from_binary(prime_str);
-  prime_str_ = prime_str.str();
-
-  b_ = BigNum();
-  g_b_ = BigNum();
-
-  BigNum::random(b_, 2048, -1, 0);
-
-  // g^b
-  g_int_ = g_int;
-  g_.set_value(g_int_);
-
-  BigNum::mod_exp(g_b_, g_, b_, prime_, ctx_);
-}
-
-Status DhHandshake::check_config(int32 g_int, Slice prime_str, DhCallback *callback) {
-  BigNumContext ctx;
-  auto prime = BigNum::from_binary(prime_str);
-  return check_config(prime_str, prime, g_int, ctx, callback);
-}
-
-void DhHandshake::set_g_a_hash(Slice g_a_hash) {
-  has_g_a_hash_ = true;
-  ok_g_a_hash_ = false;
-  CHECK(!has_g_a_);
-  g_a_hash_ = g_a_hash.str();
-}
-
-void DhHandshake::set_g_a(Slice g_a_str) {
-  has_g_a_ = true;
-  if (has_g_a_hash_) {
-    string g_a_hash(32, ' ');
-    sha256(g_a_str, g_a_hash);
-    ok_g_a_hash_ = g_a_hash == g_a_hash_;
-  }
-  g_a_ = BigNum::from_binary(g_a_str);
-}
-
-string DhHandshake::get_g_a() const {
-  CHECK(has_g_a_);
-  return g_a_.to_binary();
-}
-
-string DhHandshake::get_g_b() const {
-  CHECK(has_config_);
-  return g_b_.to_binary();
-}
-string DhHandshake::get_g_b_hash() const {
-  string g_b_hash(32, ' ');
-  sha256(get_g_b(), g_b_hash);
-  return g_b_hash;
-}
-
-Status DhHandshake::run_checks(bool skip_config_check, DhCallback *callback) {
-  CHECK(has_g_a_ && has_config_);
-
-  if (has_g_a_hash_ && !ok_g_a_hash_) {
-    return Status::Error("g_a_hash mismatch");
-  }
-
-  if (!skip_config_check) {
-    TRY_STATUS(check_config(prime_str_, prime_, g_int_, ctx_, callback));
-  }
-
-  return dh_check(prime_, g_a_, g_b_);
-}
-
-BigNum DhHandshake::get_g() const {
-  CHECK(has_config_);
-  return g_;
-}
-
-BigNum DhHandshake::get_p() const {
-  CHECK(has_config_);
-  return prime_;
-}
-
-BigNum DhHandshake::get_b() const {
-  CHECK(has_config_);
-  return b_;
-}
-
-BigNum DhHandshake::get_g_ab() {
-  CHECK(has_g_a_ && has_config_);
-  BigNum g_ab;
-  BigNum::mod_exp(g_ab, g_a_, b_, prime_, ctx_);
-  return g_ab;
-}
-
-std::pair<int64, string> DhHandshake::gen_key() {
-  string key = get_g_ab().to_binary(2048 / 8);
-  auto key_id = calc_key_id(key);
-  return std::pair<int64, string>(key_id, std::move(key));
-}
-
-int64 DhHandshake::calc_key_id(Slice auth_key) {
-  UInt<160> auth_key_sha1;
-  sha1(auth_key, auth_key_sha1.raw);
-  return as<int64>(auth_key_sha1.raw + 12);
-}
-
 /*** KDF ***/
 void KDF(const string &auth_key, const UInt128 &msg_key, int X, UInt256 *aes_key, UInt256 *aes_iv) {
   CHECK(auth_key.size() == 2048 / 8);
@@ -434,4 +224,5 @@ void KDF2(Slice auth_key, const UInt128 &msg_key, int X, UInt256 *aes_key, UInt2
   aes_iv_slice.substr(8).copy_from(sha256_a.substr(8, 16));
   aes_iv_slice.substr(24).copy_from(sha256_b.substr(24, 8));
 }
+
 }  // namespace td
diff --git a/td/mtproto/crypto.h b/td/mtproto/crypto.h
index fd0960a33..5552ffb21 100644
--- a/td/mtproto/crypto.h
+++ b/td/mtproto/crypto.h
@@ -42,123 +42,6 @@ class PublicRsaKeyInterface {
   virtual void drop_keys() = 0;
 };
 
-/*** DH ***/
-class DhCallback {
- public:
-  DhCallback() = default;
-  DhCallback(const DhCallback &) = delete;
-  DhCallback &operator=(const DhCallback &) = delete;
-  DhCallback(DhCallback &&) = delete;
-  DhCallback &operator=(DhCallback &&) = delete;
-  virtual ~DhCallback() = default;
-
-  virtual int is_good_prime(Slice prime_str) const = 0;
-  virtual void add_good_prime(Slice prime_str) const = 0;
-  virtual void add_bad_prime(Slice prime_str) const = 0;
-};
-
-class DhHandshake {
- public:
-  void set_config(int32 g_int, Slice prime_str);
-
-  static Status check_config(int32 g_int, Slice prime_str, DhCallback *callback);
-
-  bool has_config() const {
-    return has_config_;
-  }
-  void set_g_a_hash(Slice g_a_hash);
-  void set_g_a(Slice g_a_str);
-  bool has_g_a() const {
-    return has_g_a_;
-  }
-  string get_g_a() const;
-  string get_g_b() const;
-  string get_g_b_hash() const;
-  Status run_checks(bool skip_config_check, DhCallback *callback) TD_WARN_UNUSED_RESULT;
-
-  BigNum get_g() const;
-  BigNum get_p() const;
-  BigNum get_b() const;
-  BigNum get_g_ab();
-
-  std::pair<int64, string> gen_key();
-
-  static int64 calc_key_id(Slice auth_key);
-
-  enum Flags { HasConfig = 1, HasGA = 2 };
-
-  template <class StorerT>
-  void store(StorerT &storer) const {
-    auto flags = 0;
-    if (has_config_) {
-      flags |= HasConfig;
-    }
-    if (has_g_a_) {
-      flags |= HasGA;
-    }
-    storer.store_int(flags);
-
-    if (has_config_) {
-      // prime_, prime_str_, b_, g_, g_int_, g_b_
-      storer.store_string(prime_str_);
-      storer.store_string(b_.to_binary());
-      storer.store_int(g_int_);
-      storer.store_string(g_b_.to_binary());
-    }
-    if (has_g_a_) {
-      storer.store_string(g_a_.to_binary());
-    }
-  }
-  template <class ParserT>
-  void parse(ParserT &parser) {
-    auto flags = parser.fetch_int();
-    if (flags & HasConfig) {
-      has_config_ = true;
-    }
-    if (flags & HasGA) {
-      has_g_a_ = true;
-    }
-    if (has_config_) {
-      // prime_, prime_str_, b_, g_, g_int_, g_b_
-      prime_str_ = parser.template fetch_string<std::string>();
-      prime_ = BigNum::from_binary(prime_str_);
-
-      b_ = BigNum::from_binary(parser.template fetch_string<string>());
-
-      g_int_ = parser.fetch_int();
-      g_.set_value(g_int_);
-
-      g_b_ = BigNum::from_binary(parser.template fetch_string<string>());
-    }
-    if (has_g_a_) {
-      g_a_ = BigNum::from_binary(parser.template fetch_string<string>());
-    }
-  }
-
- private:
-  static Status check_config(Slice prime_str, const BigNum &prime, int32 g_int, BigNumContext &ctx,
-                             DhCallback *callback) TD_WARN_UNUSED_RESULT;
-
-  static Status dh_check(const BigNum &prime, const BigNum &g_a, const BigNum &g_b) TD_WARN_UNUSED_RESULT;
-
-  string prime_str_;
-  BigNum prime_;
-  BigNum g_;
-  int32 g_int_;
-  BigNum b_;
-  BigNum g_b_;
-  BigNum g_a_;
-
-  string g_a_hash_;
-  bool has_g_a_hash_{false};
-  bool ok_g_a_hash_{false};
-
-  bool has_config_ = false;
-  bool has_g_a_ = false;
-
-  BigNumContext ctx_;
-};
-
 /*** KDF ***/
 void KDF(const string &auth_key, const UInt128 &msg_key, int X, UInt256 *aes_key, UInt256 *aes_iv);
 void tmp_KDF(const UInt128 &server_nonce, const UInt256 &new_nonce, UInt256 *tmp_aes_key, UInt256 *tmp_aes_iv);
diff --git a/td/telegram/CallActor.cpp b/td/telegram/CallActor.cpp
index 172bd2e45..ce7267e70 100644
--- a/td/telegram/CallActor.cpp
+++ b/td/telegram/CallActor.cpp
@@ -10,8 +10,6 @@
 #include "td/telegram/telegram_api.h"
 #include "td/telegram/telegram_api.hpp"
 
-#include "td/mtproto/crypto.h"
-
 #include "td/telegram/ConfigShared.h"
 #include "td/telegram/ContactsManager.h"
 #include "td/telegram/DhCache.h"
diff --git a/td/telegram/CallActor.h b/td/telegram/CallActor.h
index 452de3294..1467c0ac5 100644
--- a/td/telegram/CallActor.h
+++ b/td/telegram/CallActor.h
@@ -9,7 +9,7 @@
 #include "td/telegram/td_api.h"
 #include "td/telegram/telegram_api.h"
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/telegram/CallDiscardReason.h"
 #include "td/telegram/CallId.h"
diff --git a/td/telegram/DeviceTokenManager.cpp b/td/telegram/DeviceTokenManager.cpp
index 2f6afd8da..00b0f0424 100644
--- a/td/telegram/DeviceTokenManager.cpp
+++ b/td/telegram/DeviceTokenManager.cpp
@@ -15,7 +15,7 @@
 #include "td/telegram/td_api.hpp"
 #include "td/telegram/telegram_api.h"
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/utils/base64.h"
 #include "td/utils/buffer.h"
diff --git a/td/telegram/DhCache.h b/td/telegram/DhCache.h
index e8042b10b..29cd26db8 100644
--- a/td/telegram/DhCache.h
+++ b/td/telegram/DhCache.h
@@ -6,7 +6,7 @@
 //
 #pragma once
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/utils/Slice.h"
 
diff --git a/td/telegram/PasswordManager.cpp b/td/telegram/PasswordManager.cpp
index 1c83d4b05..9b65e6bd6 100644
--- a/td/telegram/PasswordManager.cpp
+++ b/td/telegram/PasswordManager.cpp
@@ -13,7 +13,7 @@
 #include "td/telegram/SecureStorage.h"
 #include "td/telegram/TdDb.h"
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/utils/BigNum.h"
 #include "td/utils/buffer.h"
diff --git a/td/telegram/SecretChatActor.h b/td/telegram/SecretChatActor.h
index d57c28d2b..682902c3c 100644
--- a/td/telegram/SecretChatActor.h
+++ b/td/telegram/SecretChatActor.h
@@ -13,7 +13,7 @@
 #include "td/actor/PromiseFuture.h"
 
 #include "td/mtproto/AuthKey.h"
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/telegram/DhConfig.h"
 #include "td/telegram/logevent/SecretChatEvent.h"
diff --git a/td/telegram/SecretChatsManager.cpp b/td/telegram/SecretChatsManager.cpp
index 967ac59a5..704ba5112 100644
--- a/td/telegram/SecretChatsManager.cpp
+++ b/td/telegram/SecretChatsManager.cpp
@@ -22,7 +22,7 @@
 #include "td/telegram/secret_api.h"
 #include "td/telegram/telegram_api.hpp"
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 
 #include "td/actor/PromiseFuture.h"
 
diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index c77664ebf..bd3d55625 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -18,6 +18,7 @@
 #include "td/telegram/UniqueId.h"
 
 #include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 #include "td/mtproto/Handshake.h"
 #include "td/mtproto/HandshakeActor.h"
 #include "td/mtproto/RawConnection.h"
diff --git a/test/mtproto.cpp b/test/mtproto.cpp
index 2b280596b..403e77725 100644
--- a/test/mtproto.cpp
+++ b/test/mtproto.cpp
@@ -10,11 +10,11 @@
 #include "td/actor/PromiseFuture.h"
 
 #include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 #include "td/mtproto/Handshake.h"
 #include "td/mtproto/HandshakeActor.h"
 #include "td/mtproto/PingConnection.h"
 #include "td/mtproto/RawConnection.h"
-#include "td/mtproto/Transport.h"
 #include "td/mtproto/TransportType.h"
 
 #include "td/net/GetHostByNameActor.h"
diff --git a/test/secret.cpp b/test/secret.cpp
index 175d8e78e..bb5584d25 100644
--- a/test/secret.cpp
+++ b/test/secret.cpp
@@ -20,7 +20,7 @@
 #include "td/db/BinlogKeyValue.h"
 #include "td/db/DbKey.h"
 
-#include "td/mtproto/crypto.h"
+#include "td/mtproto/DhHandshake.h"
 #include "td/mtproto/utils.h"
 
 #include "td/tl/tl_object_parse.h"