Removed ARC4Decryptor because ARC4Encryptor can decrypt the message.

15 files changed, 21 insertions, 480 deletions

diff --git a/src/ARC4Decryptor.h b/src/ARC4Decryptor.h
deleted file mode 100644
index c2cb4c29..00000000
--- a/src/ARC4Decryptor.h
+++ /dev/null
@@ -1,67 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef D_ARC4_DECRYPTOR_H
-#define D_ARC4_DECRYPTOR_H
-
-#include "common.h"
-#ifdef HAVE_LIBNETTLE
-# include "LibnettleARC4Decryptor.h"
-#elif HAVE_LIBGCRYPT
-# include "LibgcryptARC4Decryptor.h"
-#elif HAVE_OPENSSL
-# include "LibsslARC4Decryptor.h"
-#else
-
-// provide empty implementation to compile sources without both libgcrypt and
-// openssl installed
-namespace aria2 {
-
-class ARC4Decryptor {
-public:
-  ARC4Decryptor() {}
-
-  ~ARC4Decryptor() {}
-
-  void init(const unsigned char* key, size_t keyLength) {}
-
-  void decrypt(unsigned char* out, size_t outLength,
-               const unsigned char* in, size_t inLength) {}
-};
-
-} // namespace aria2
-
-#endif
-
-#endif // D_ARC4_DECRYPTOR_H
diff --git a/src/InitiatorMSEHandshakeCommand.cc b/src/InitiatorMSEHandshakeCommand.cc
index e76a7336..cf82858e 100644
--- a/src/InitiatorMSEHandshakeCommand.cc
+++ b/src/InitiatorMSEHandshakeCommand.cc
@@ -50,7 +50,6 @@
 #include "Option.h"
 #include "MSEHandshake.h"
 #include "ARC4Encryptor.h"
-#include "ARC4Decryptor.h"
 #include "RequestGroup.h"
 #include "DownloadContext.h"
 #include "bittorrent_helper.h"
@@ -158,7 +157,7 @@ bool InitiatorMSEHandshakeCommand::executeInternal() {
                                            mseHandshake_->getDecryptor());
           size_t buflen = mseHandshake_->getBufferLength();
           array_ptr<unsigned char> buffer(new unsigned char[buflen]);
-          mseHandshake_->getDecryptor()->decrypt(buffer, buflen,
+          mseHandshake_->getDecryptor()->encrypt(buffer, buflen,
                                                  mseHandshake_->getBuffer(),
                                                  buflen);
           peerConnection->presetBuffer(buffer, buflen);
diff --git a/src/LibgcryptARC4Decryptor.cc b/src/LibgcryptARC4Decryptor.cc
deleted file mode 100644
index 2515bb10..00000000
--- a/src/LibgcryptARC4Decryptor.cc
+++ /dev/null
@@ -1,72 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2010 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#include "LibgcryptARC4Decryptor.h"
-
-#include <gcrypt.h>
-
-#include "DlAbortEx.h"
-#include "fmt.h"
-
-namespace aria2 {
-
-namespace {
-void handleError(gcry_error_t err)
-{
-  throw DL_ABORT_EX
-    (fmt("Exception in libgcrypt routine(ARC4Decryptor class): %s",
-         gcry_strerror(err)));
-}
-} // namespace
-
-ARC4Decryptor::ARC4Decryptor() {}
-
-ARC4Decryptor::~ARC4Decryptor() {}
-
-void ARC4Decryptor::init(const unsigned char* key, size_t keyLength)
-{
-  ctx_.init(key, keyLength);
-}
-
-void ARC4Decryptor::decrypt
-(unsigned char* out, size_t outLength, const unsigned char* in, size_t inLength)
-{
-  gcry_error_t r = gcry_cipher_decrypt(ctx_.getCipherContext(),
-                                       out, outLength, in, inLength);
-  if(r) {
-    handleError(r);
-  }
-}
-
-} // namespace aria2
diff --git a/src/LibgcryptARC4Decryptor.h b/src/LibgcryptARC4Decryptor.h
deleted file mode 100644
index 738528d7..00000000
--- a/src/LibgcryptARC4Decryptor.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef D_LIBGCRYPT_ARC4_DECRYPTOR_H
-#define D_LIBGCRYPT_ARC4_DECRYPTOR_H
-
-#include "common.h"
-#include "LibgcryptARC4Context.h"
-
-namespace aria2 {
-
-class ARC4Decryptor {
-private:
-  LibgcryptARC4Context ctx_;
-public:
-  ARC4Decryptor();
-
-  ~ARC4Decryptor();
-
-  void init(const unsigned char* key, size_t keyLength);
-
-  void decrypt(unsigned char* out, size_t outLength,
-               const unsigned char* in, size_t inLength);
-};
-
-} // namespace aria2
-
-#endif // D_LIBGCRYPT_ARC4_DECRYPTOR_H
diff --git a/src/LibnettleARC4Decryptor.cc b/src/LibnettleARC4Decryptor.cc
deleted file mode 100644
index e79a21bf..00000000
--- a/src/LibnettleARC4Decryptor.cc
+++ /dev/null
@@ -1,57 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2011 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#include "LibnettleARC4Decryptor.h"
-
-#include <cassert>
-
-namespace aria2 {
-
-ARC4Decryptor::ARC4Decryptor() {}
-
-ARC4Decryptor::~ARC4Decryptor() {}
-
-void ARC4Decryptor::init(const unsigned char* key, size_t keyLength)
-{
-  ctx_.init(key, keyLength);
-}
-
-void ARC4Decryptor::decrypt(unsigned char* out, size_t outLength,
-                            const unsigned char* in, size_t inLength)
-{
-  assert(outLength == inLength);
-  arcfour_crypt(ctx_.getCipherContext(), outLength, out, in);
-}
-
-} // namespace aria2
diff --git a/src/LibnettleARC4Decryptor.h b/src/LibnettleARC4Decryptor.h
deleted file mode 100644
index fab17cdb..00000000
--- a/src/LibnettleARC4Decryptor.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2011 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef D_LIBNETTLE_ARC4_DECRYPTOR_H
-#define D_LIBNETTLE_ARC4_DECRYPTOR_H
-
-#include "common.h"
-#include "LibnettleARC4Context.h"
-
-namespace aria2 {
-
-class ARC4Decryptor {
-private:
-  LibnettleARC4Context ctx_;
-public:
-  ARC4Decryptor();
-
-  ~ARC4Decryptor();
-
-  void init(const unsigned char* key, size_t keyLength);
-
-  void decrypt(unsigned char* out, size_t outLength,
-               const unsigned char* in, size_t inLength);
-};
-
-} // namespace aria2
-
-#endif // D_LIBNETTLE_ARC4_DECRYPTOR_H
diff --git a/src/LibsslARC4Decryptor.cc b/src/LibsslARC4Decryptor.cc
deleted file mode 100644
index 7af932d4..00000000
--- a/src/LibsslARC4Decryptor.cc
+++ /dev/null
@@ -1,72 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2010 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#include "LibsslARC4Decryptor.h"
-
-#include <openssl/err.h>
-
-#include "DlAbortEx.h"
-#include "fmt.h"
-
-namespace aria2 {
-
-namespace {
-void handleError()
-{
-  throw DL_ABORT_EX
-    (fmt("Exception in libssl routine(ARC4Decryptor class): %s",
-         ERR_error_string(ERR_get_error(), 0)));
-}
-} // namespace
-
-ARC4Decryptor::ARC4Decryptor() {}
-
-ARC4Decryptor::~ARC4Decryptor() {}
-
-void ARC4Decryptor::init(const unsigned char* key, size_t keyLength)
-{
-  ctx_.init(key, keyLength, 0);
-}
-
-void ARC4Decryptor::decrypt(unsigned char* out, size_t outLength,
-                            const unsigned char* in, size_t inLength)
-{
-  int soutLength = outLength;
-  if(!EVP_CipherUpdate(ctx_.getCipherContext(), out, &soutLength,
-                       in, inLength)) {
-    handleError();
-  }
-}
-
-} // namespace aria2
diff --git a/src/LibsslARC4Decryptor.h b/src/LibsslARC4Decryptor.h
deleted file mode 100644
index 53e591c7..00000000
--- a/src/LibsslARC4Decryptor.h
+++ /dev/null
@@ -1,62 +0,0 @@
-/* <!-- copyright */
-/*
- * aria2 - The high speed download utility
- *
- * Copyright (C) 2006 Tatsuhiro Tsujikawa
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * In addition, as a special exception, the copyright holders give
- * permission to link the code of portions of this program with the
- * OpenSSL library under certain conditions as described in each
- * individual source file, and distribute linked combinations
- * including the two.
- * You must obey the GNU General Public License in all respects
- * for all of the code used other than OpenSSL.  If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so.  If you
- * do not wish to do so, delete this exception statement from your
- * version.  If you delete this exception statement from all source
- * files in the program, then also delete it here.
- */
-/* copyright --> */
-#ifndef D_LIBSSL_ARC4_DECRYPTOR_H
-#define D_LIBSSL_ARC4_DECRYPTOR_H
-
-#include "common.h"
-
-#include <openssl/evp.h>
-
-#include "LibsslARC4Context.h"
-
-namespace aria2 {
-
-class ARC4Decryptor {
-private:
-  LibsslARC4Context ctx_;
-public:
-  ARC4Decryptor();
-
-  ~ARC4Decryptor();
-
-  void init(const unsigned char* key, size_t keyLength);
-
-  void decrypt(unsigned char* out, size_t outLength,
-               const unsigned char* in, size_t inLength);
-};
-
-} // namespace aria2
-
-#endif // D_LIBSSL_ARC4_DECRYPTOR_H
diff --git a/src/MSEHandshake.cc b/src/MSEHandshake.cc
index 861ae1f9..74080feb 100644
--- a/src/MSEHandshake.cc
+++ b/src/MSEHandshake.cc
@@ -46,7 +46,6 @@
 #include "a2netcompat.h"
 #include "DHKeyExchange.h"
 #include "ARC4Encryptor.h"
-#include "ARC4Decryptor.h"
 #include "MessageDigest.h"
 #include "message_digest_helper.h"
 #include "SimpleRandomizer.h"
@@ -204,14 +203,14 @@ void MSEHandshake::initCipher(const unsigned char* infoHash)
   sha1_->reset();
   message_digest::digest(peerCipherKey, sizeof(peerCipherKey),
                          sha1_, s, sizeof(s));
-  decryptor_.reset(new ARC4Decryptor());
+  decryptor_.reset(new ARC4Encryptor());
   decryptor_->init(peerCipherKey, sizeof(peerCipherKey));
 
   // discard first 1024 bytes ARC4 output.
   unsigned char from[1024];
   unsigned char to[1024];
   encryptor_->encrypt(to, 1024, from, 1024);
-  decryptor_->decrypt(to, 1024, from, 1024);
+  decryptor_->encrypt(to, 1024, from, 1024);
 
   if(initiator_) {
     ARC4Encryptor enc;
@@ -264,7 +263,7 @@ void MSEHandshake::createReq23Hash(unsigned char* md, const unsigned char* infoH
 uint16_t MSEHandshake::decodeLength16(const unsigned char* buffer)
 {
   uint16_t be;
-  decryptor_->decrypt(reinterpret_cast<unsigned char*>(&be),
+  decryptor_->encrypt(reinterpret_cast<unsigned char*>(&be),
                       sizeof(be),
                       buffer, sizeof(be));
   return ntohs(be);
@@ -355,7 +354,7 @@ bool MSEHandshake::receiveInitiatorCryptoSelectAndPadDLength()
   unsigned char* rbufptr = rbuf_;
   {
     unsigned char cryptoSelect[CRYPTO_BITFIELD_LENGTH];
-    decryptor_->decrypt(cryptoSelect, sizeof(cryptoSelect),
+    decryptor_->encrypt(cryptoSelect, sizeof(cryptoSelect),
                         rbufptr, sizeof(cryptoSelect));
     if(cryptoSelect[3]&CRYPTO_PLAIN_TEXT &&
        option_->get(PREF_BT_MIN_CRYPTO_LEVEL) == V_PLAIN) {
@@ -392,7 +391,7 @@ bool MSEHandshake::receivePad()
     return true;
   }
   unsigned char temp[MAX_PAD_LENGTH];
-  decryptor_->decrypt(temp, padLength_, rbuf_, padLength_);
+  decryptor_->encrypt(temp, padLength_, rbuf_, padLength_);
   // shift rbuf_
   shiftBuffer(padLength_);
   return true;
@@ -459,7 +458,7 @@ bool MSEHandshake::receiveReceiverHashAndPadCLength
   rbufptr += VC_LENGTH;
   {
     unsigned char cryptoProvide[CRYPTO_BITFIELD_LENGTH];
-    decryptor_->decrypt(cryptoProvide, sizeof(cryptoProvide),
+    decryptor_->encrypt(cryptoProvide, sizeof(cryptoProvide),
                         rbufptr, sizeof(cryptoProvide));
     // TODO choose the crypto type based on the preference.
     // For now, choose ARC4.
@@ -514,7 +513,7 @@ bool MSEHandshake::receiveReceiverIA()
   }
   delete [] ia_;
   ia_ = new unsigned char[iaLength_];
-  decryptor_->decrypt(ia_, iaLength_, rbuf_, iaLength_);
+  decryptor_->encrypt(ia_, iaLength_, rbuf_, iaLength_);
   A2_LOG_DEBUG(fmt("CUID#%lld - IA received.", cuid_));
   // shift rbuf_
   shiftBuffer(iaLength_);
@@ -566,7 +565,7 @@ void MSEHandshake::verifyVC(const unsigned char* vcbuf)
 {
   A2_LOG_DEBUG(fmt("CUID#%lld - Verifying VC.", cuid_));
   unsigned char vc[VC_LENGTH];
-  decryptor_->decrypt(vc, sizeof(vc), vcbuf, sizeof(vc));
+  decryptor_->encrypt(vc, sizeof(vc), vcbuf, sizeof(vc));
   if(memcmp(VC, vc, sizeof(VC)) != 0) {
     throw DL_ABORT_EX
       (fmt("Invalid VC: %s", util::toHex(vc, VC_LENGTH).c_str()));
diff --git a/src/MSEHandshake.h b/src/MSEHandshake.h
index 65801940..94e57b80 100644
--- a/src/MSEHandshake.h
+++ b/src/MSEHandshake.h
@@ -50,7 +50,6 @@ class Option;
 class SocketCore;
 class DHKeyExchange;
 class ARC4Encryptor;
-class ARC4Decryptor;
 class DownloadContext;
 class MessageDigest;
 
@@ -90,7 +89,7 @@ private:
   CRYPTO_TYPE negotiatedCryptoType_;
   DHKeyExchange* dh_;
   SharedHandle<ARC4Encryptor> encryptor_;
-  SharedHandle<ARC4Decryptor> decryptor_;
+  SharedHandle<ARC4Encryptor> decryptor_;
   unsigned char infoHash_[INFO_HASH_LENGTH];
   unsigned char secret_[KEY_LENGTH];
   bool initiator_;
@@ -203,7 +202,7 @@ public:
     return encryptor_;
   }
 
-  const SharedHandle<ARC4Decryptor>& getDecryptor() const
+  const SharedHandle<ARC4Encryptor>& getDecryptor() const
   {
     return decryptor_;
   }
diff --git a/src/Makefile.am b/src/Makefile.am
index eeec254b..85dc6f05 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -265,7 +265,6 @@ endif # HAVE_LIBGNUTLS
 if HAVE_LIBGCRYPT
 SRCS += LibgcryptMessageDigestImpl.cc LibgcryptMessageDigestImpl.h\
 	LibgcryptARC4Context.cc LibgcryptARC4Context.h\
-	LibgcryptARC4Decryptor.cc LibgcryptARC4Decryptor.h\
 	LibgcryptARC4Encryptor.cc LibgcryptARC4Encryptor.h\
 	LibgcryptDHKeyExchange.cc LibgcryptDHKeyExchange.h
 endif # HAVE_LIBGCRYPT
@@ -273,7 +272,6 @@ endif # HAVE_LIBGCRYPT
 if HAVE_LIBNETTLE
 SRCS += LibnettleMessageDigestImpl.cc LibnettleMessageDigestImpl.h\
 	LibnettleARC4Context.cc LibnettleARC4Context.h\
-	LibnettleARC4Decryptor.cc LibnettleARC4Decryptor.h\
 	LibnettleARC4Encryptor.cc LibnettleARC4Encryptor.h
 endif # HAVE_LIBNETTLE
 
@@ -286,7 +284,6 @@ if HAVE_OPENSSL
 SRCS += LibsslTLSContext.cc LibsslTLSContext.h\
 	LibsslMessageDigestImpl.cc LibsslMessageDigestImpl.h\
 	LibsslARC4Context.cc LibsslARC4Context.h\
-	LibsslARC4Decryptor.cc LibsslARC4Decryptor.h\
 	LibsslARC4Encryptor.cc LibsslARC4Encryptor.h\
 	LibsslDHKeyExchange.cc LibsslDHKeyExchange.h
 endif # HAVE_OPENSSL
@@ -466,7 +463,6 @@ SRCS += PeerAbstractCommand.cc PeerAbstractCommand.h\
 	InitiatorMSEHandshakeCommand.cc InitiatorMSEHandshakeCommand.h\
 	ReceiverMSEHandshakeCommand.cc ReceiverMSEHandshakeCommand.h\
 	MSEHandshake.cc MSEHandshake.h\
-	ARC4Decryptor.h\
 	ARC4Encryptor.h\
 	DHKeyExchange.h\
 	BtConstants.h\
diff --git a/src/PeerConnection.cc b/src/PeerConnection.cc
index b894f8ae..6a3320fb 100644
--- a/src/PeerConnection.cc
+++ b/src/PeerConnection.cc
@@ -46,7 +46,6 @@
 #include "Socket.h"
 #include "a2netcompat.h"
 #include "ARC4Encryptor.h"
-#include "ARC4Decryptor.h"
 #include "fmt.h"
 #include "util.h"
 #include "Peer.h"
@@ -216,7 +215,7 @@ void PeerConnection::readData
     unsigned char temp[MAX_PAYLOAD_LEN];
     assert(MAX_PAYLOAD_LEN >= length);
     socket_->readData(temp, length);
-    decryptor_->decrypt(data, length, temp, length);
+    decryptor_->encrypt(data, length, temp, length);
   } else {
     socket_->readData(data, length);
   }
@@ -224,7 +223,7 @@ void PeerConnection::readData
 
 void PeerConnection::enableEncryption
 (const SharedHandle<ARC4Encryptor>& encryptor,
- const SharedHandle<ARC4Decryptor>& decryptor)
+ const SharedHandle<ARC4Encryptor>& decryptor)
 {
   encryptor_ = encryptor;
   decryptor_ = decryptor;
diff --git a/src/PeerConnection.h b/src/PeerConnection.h
index 15676381..3da56eb4 100644
--- a/src/PeerConnection.h
+++ b/src/PeerConnection.h
@@ -48,7 +48,6 @@ namespace aria2 {
 class Peer;
 class SocketCore;
 class ARC4Encryptor;
-class ARC4Decryptor;
 
 // The maximum length of payload. Messages beyond that length are
 // dropped.
@@ -70,7 +69,7 @@ private:
 
   bool encryptionEnabled_;
   SharedHandle<ARC4Encryptor> encryptor_;
-  SharedHandle<ARC4Decryptor> decryptor_;
+  SharedHandle<ARC4Encryptor> decryptor_;
 
   bool prevPeek_;
 
@@ -104,7 +103,7 @@ public:
   (unsigned char* data, size_t& dataLength, bool peek = false);
 
   void enableEncryption(const SharedHandle<ARC4Encryptor>& encryptor,
-                        const SharedHandle<ARC4Decryptor>& decryptor);
+                        const SharedHandle<ARC4Encryptor>& decryptor);
 
   void presetBuffer(const unsigned char* data, size_t length);
 
diff --git a/src/ReceiverMSEHandshakeCommand.cc b/src/ReceiverMSEHandshakeCommand.cc
index da445f6d..cfde2d42 100644
--- a/src/ReceiverMSEHandshakeCommand.cc
+++ b/src/ReceiverMSEHandshakeCommand.cc
@@ -46,7 +46,6 @@
 #include "Option.h"
 #include "MSEHandshake.h"
 #include "ARC4Encryptor.h"
-#include "ARC4Decryptor.h"
 #include "RequestGroupMan.h"
 #include "BtRegistry.h"
 #include "DownloadContext.h"
diff --git a/test/ARC4Test.cc b/test/ARC4Test.cc
index 0f6b672b..9275fa49 100644
--- a/test/ARC4Test.cc
+++ b/test/ARC4Test.cc
@@ -3,7 +3,6 @@
 #include <cstring>
 #include <cppunit/extensions/HelperMacros.h>
 
-#include "ARC4Decryptor.h"
 #include "Exception.h"
 #include "util.h"
 
@@ -12,23 +11,23 @@ namespace aria2 {
 class ARC4Test:public CppUnit::TestFixture {
 
   CPPUNIT_TEST_SUITE(ARC4Test);
-  CPPUNIT_TEST(testEncryptDecrypt);
+  CPPUNIT_TEST(testEncrypt);
   CPPUNIT_TEST_SUITE_END();
 public:
   void setUp() {}
 
   void tearDown() {}
 
-  void testEncryptDecrypt();
+  void testEncrypt();
 };
 
 
 CPPUNIT_TEST_SUITE_REGISTRATION(ARC4Test);
 
-void ARC4Test::testEncryptDecrypt()
+void ARC4Test::testEncrypt()
 {
   ARC4Encryptor enc;
-  ARC4Decryptor dec;
+  ARC4Encryptor dec;
   const size_t LEN = 20;
   unsigned char key[LEN];
   memset(key, 0, LEN);
@@ -39,12 +38,12 @@ void ARC4Test::testEncryptDecrypt()
   unsigned char encrypted[LEN];
   unsigned char decrypted[LEN];
   enc.encrypt(encrypted, LEN, key, LEN);
-  dec.decrypt(decrypted, LEN, encrypted, LEN);
+  dec.encrypt(decrypted, LEN, encrypted, LEN);
 
   CPPUNIT_ASSERT(memcmp(key, decrypted, LEN) == 0);
   // once more
   enc.encrypt(encrypted, LEN, key, LEN);
-  dec.decrypt(decrypted, LEN, encrypted, LEN);
+  dec.encrypt(decrypted, LEN, encrypted, LEN);
 
   CPPUNIT_ASSERT(memcmp(key, decrypted, LEN) == 0);
 }