Copyright (C) 2017, 2018, 2019, 2020  Heiko Stamer <HeikoStamer@gmx.net>  Permission is granted to copy, distribute and/or modify this document  under the terms of the GNU Free Documentation License, Version 1.3  or any later version published by the Free Software Foundation;  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover  Texts. A copy of the license is included in the section entitled  "APPENDIX: GNU Free Documentation License".Introduction------------  Distributed Privacy Guard (DKGPG) implements Distributed Key Generation (DKG)  and Threshold Cryptography for OpenPGP. The generated public keys are  compatible with the standard and thus can be used by any RFC4880-compliant  application (e.g. GnuPG). The main purposes of this software are distributing  power among multiple parties, eliminating single points of failure, and  increasing the difficulty of side-channel attacks on private key material.  Using well-established multi-party protocols a shared private key and a  common public key (DSA/ElGamal) are generated. Then further interactive  protocols perform the private operations like decryption of messages and  signing of files or keys, provided that a previously defined threshold of  parties/devices take part in the distributed computation. For completeness  DKGPG contains programs for public-key encryption and signature verification.  The security is based on the well-established cryptographic assumption that  computing discrete logarithms in large prime order subgroups of Z_p (finite  field) is hard. The current implementation is still experimental and should  NOT be used for production, because it has been not yet reviewed by an  independend third party. Some details about design criteria can be found in  these presentation slides:http://www.nongnu.org/libtmcg/dg81_slides.pdf  DKGPG is 'Free Software' according to the definition of the Free Software  Foundation. The source code is released under the GNU General Public License.Overview--------  Distributed Privacy Guard consists of a bunch of command-line programs:   The program dkg-generate provides an implementation of distributed key share  generation for DSA/DSS and the ElGamal cryptosystem. The generation and the  refresh (the latter is done by a separated program called dkg-refresh) needs  a lot of strong quality randomness (see e.g. D. Eastlake, J. Schiller, and  S. Crocker: Randomness Requirements for Security, Network Working Group,  Request for Comments: 4086, June 2005) obtained by DKGPG from the GNU Crypto  Library (libgcrypt), that means, the execution will slow down or even fail on  systems (e.g. headless servers) if only low entropy sources for /dev/random  (i.e. the source of strong randomness for libgcrypt) are available. The random  number generation, input/output operations, arithmetic functions, OpenPGP  support, and some high-level protocols are provided by another library of the  author, i.e., Toolbox for Mental Card Games (LibTMCG). If this LibTMCG is  built with optional support of Botan (another C++ crypto library), then the  aquired random numbers incorporate randomness from Botan::AutoSeeded_RNG as  an additional source to rely not only on libgcrypt's RNG implementation.  Due to the interactiveness of the protocols a lot of messages resp. data have  to be exchanged between participating parties in a secure way. We employ  GNUnet, and in particular its mesh routed CADET service, to establish private  point-to-point and separated broadcast channels for this message exchange.  A so-called reliable broadcast protocol (RBC) from LibTMCG is used as a weak  mechanism to achieve some validity, consistency, and totality in a most  likely asynchronous communication environment. However, there are limitations  (termination is not guaranteed) and predefined timeout values. Timing problems  may be recognized by looking for error messages with prefix "RBC" on STDERR  output of the interactive programs. In such cases the predefined timeout  value (default: five minutes) can be adjusted by using option "-W".  The program dkg-encrypt encrypts a text message for a given public key in  OpenPGP format. It uses AES256 as fixed symmetric cipher and most of the  public-key algorithms defined by OpenPGP, even AEAD algorithms from draft  RFC 4880bis, if they are supported by libgcrypt. Of course, a similar result  can be achieved by any OpenPGP-compatible implementation --- the program is  only included for completeness. Conversely, a corresponding threshold  decryption protocol (see Ronald Cramer, Rosario Gennaro, and Berry  Schoenmakers: A Secure and Optimally Efficient Multi-Authority Election  Scheme, Advances in Cryptology – EUROCRYPT ’97, LNCS 1233, pp. 103–118, 1997)  has been implemented by the program dkg-decrypt. It provides an interactive  version and a non-interactive version for computing, verifying, and combining  the required decryption shares from participating players. Finally, if  everything is sane, it outputs the decrypted message. The included OpenPGP  signatures can be verified by using the option "-k" with a keyring that  contains the required public keys.  Since version 1.0.8 most DKGPG programs support a new option "-y" that turns  them into a regular OpenPGP implementation operating with any transferable  private key (ASCII-armored format). For example, this option is available for  dkg-generate, dkg-decrypt, dkg-sign, dkg-keysign, and dkg-timestamp.  The programs dkg-keycheck and dkg-keyinfo print some basic information for a  given OpenPGP public and private key, respectively. However, there is another  special use case for DKGPG: The option "-m" of dkg-keyinfo migrates a changed  peer identity, if the new name meets some requirements. Note that only the  name of the peer is migrated, other parts of the private key material are not  changed.    The private key shares of all active parties should be changed regularly by  program dkg-refresh. Each player who does not join this refresh process is  excluded from any further operation with the shared private key.  The program dkg-sign creates a detached signature on a binary or a text file,  if a sufficient threshold of the parties work together in the interactive  signing protocol. Such a detached signature can be verified with any OpenPGP-  compatible software or the included programm dkg-verify. Thus DKGPG solves  the problem of distributed code-signing without secret key splitting (e.g.  libgfshare) and laborious reconstruction ceremonies (e.g. as used for DNSSEC  root signing key). The program dkg-keysign generates certification signatures  in a similar manner for each selected and valid user ID of a given public key.  User attributes are not supported yet. With the program dkg-adduid an  additional user ID can be created and with dkg-revuid a present user ID can be  revoked. The program dkg-addrevoker creates a direct-key signature which  specifies an external key (given by option "-i") that can act as an additional  revoker. Last but not least, the program dkg-revoke generates corresponding  revocation signatures (also known as revocation certificates) for the key.  Please consult the manual pages for detailed information on usage and options.  Note that for building GNUnet support of dkg-generate, dkg-adduid, dkg-revuid,  dkg-refresh, dkg-sign, dkg-keysign, dkg-timestamp, dkg-addrevoker, dkg-revoke,  and the interactive version of dkg-decrypt the development files and a working  environment of a very recent version (at least 0.11.x series) must be present.  However, as simple workaround for systems without GNUnet a TCP/IP-based  mechanism for message exchange is included (option "-H <hostname>") in each  program that needs network interaction. To keep confidentiality and integrity  of the established point-to-point channels some mutually chosen and (manually)  distributed passwords (option "-P <password list>") are required. The format  of such a password list is explained in the corresponding manual pages.  Moreover, with torsocks and some obvious port forwarding rules for a hidden  service (see manual page of dkg-generarte for the details) this mechanism  allows running the interactive DKGPG programs over Tor.Requirements------------  You need the following programs, libraries and appropriate header files to  build (GNU gcc/g++ >= 5.4.x or higher is recommended) DKGPG successfully:  * Toolbox for Mental Card Games (LibTMCG), version >= 1.4.0https://savannah.nongnu.org/projects/libtmcg  * GNU Multiple Precision Arithmetic Library (libgmp), version >= 6.1.2,https://gmplib.org/  * GNU Crypto Library (libgcrypt), version >= 1.8.0,https://gnupg.org/download/index.html  * GNU Privacy Guard Error Code Library (libgpg-error), version >= 1.27,https://gnupg.org/download/index.html  * zlib Compression Library (libz), version >= 1.2.3https://zlib.net/  * [OPTIONAL] Library for data compression (libbzip2), version >= 1.0.6,http://www.bzip.org/  * [OPTIONAL] GNUnet, version >= 0.11.7https://gnunet.org/  The DKGPG package was tested (++ successful, -- erroneous) on the following  platforms with the given compilers, respectively:  ++ GNU/Linux (Gentoo Linux)    x86_64    gcc 10.2.0  (details omitted)  ++ GNU/Linux (Gentoo Linux)    x86_64  clang 11.0.0  (details omitted)  ++ GNU/Linux (Debian Linux)    x86_64    gcc  8.3.0  (details omitted)  ++ GNU/Linux (Trisquel Linux)  x86_64    gcc  4.8.4  (details omitted)  ++ OpenBSD 6.5                 amd64     gcc  4.2.1  (details omitted)  ++ FreeBSD 12.1                amd64   clang  8.0.1  (details omitted)Build & Install---------------  You should proceed by executing the following magic commands:    1. ./configure    2. make    3. make installBugs, Contribution, GIT-----------------------  Please send detailed bug reports to Heiko Stamer <HeikoStamer@gmx.net>,  or even better, use our bug tracker at:https://savannah.nongnu.org/bugs/?func=additem&group=dkgpg  You can get the latest sources from the source repository by using the  command    git clonehttps://git.savannah.gnu.org/git/dkgpg  The GNU C++ compiler from GCC and the GNU Make program is required.  Additionally you will need the following free software packages:    * GNU Autoconf, version >= 2.61,https://www.gnu.org/software/autoconf/  * GNU Automake, version >= 1.12,https://www.gnu.org/software/automake/  * GNU Libtool, version >= 2.4.2,https://www.gnu.org/software/libtool/Example: working configuration in .muttrc (replacement of classic pgp)----------------------------------------------------------------------[...]  unset crypt_use_gpgme  unset pgp_use_gpg_agent  set pgp_list_pubring_command="~/bin/dkg-keycheck -y -k ~/keyring.asc %r"  set pgp_self_encrypt=yes  set pgp_default_key="0x76F73011329D27DB8D7C3F974F584EB8FB2BE14F"  set pgp_encrypt_only_command="~/bin/dkg-encrypt -k ~/keyring.asc -i %f -r %r"  set pgp_check_gpg_decrypt_status_fd=no  set pgp_decryption_okay="^INFO: decrypted message"  set pgp_decrypt_command="~/bin/dkg-decrypt -E -V -k ~/keyring.asc -y ~/secretkey.asc -i %f"  set pgp_verify_command="~/bin/dkg-verify -V -k ~/keyring.asc -i %f -s %s"  set pgp_good_sign="^INFO: Good signature"  set pgp_sign_command="~/bin/dkg-sign -E -t -V -y ~/secretkey.asc -i %f"[...]Copyright and License of this software--------------------------------------  (C) 2017, 2018, 2019, 2020  Heiko Stamer <HeikoStamer@gmx.net>        GNU General Public License version 2,            or (at your option) any later version published by            the Free Software Foundation.  Please have a look at file 'COPYING' andhttps://www.fsf.org/.APPENDIX: GNU Free Documentation License----------------------------------------                GNU Free Documentation License                 Version 1.3, 3 November 2008 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.     <http://fsf.org/> Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.0. 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