Implementations different from GnuPG that aim for OpenPGP compliance.
 
**Please take care**: This is an old list of code which has been found on the Net. 
Most of the projects are niche applications or not anymore maintained


= OpenPGP.js

https://openpgpjs.org/ 

License: GNU LGPL v>=2.1.

used by:
* https://www.mailvelope.com/ (License GNU Affero v==3) for Webmail -- extensions for Chrome/Chromium & Firefox
* [[https://chrome.google.com/webstore/detail/mymail-crypt-for-gmail/jcaobjhdnlpmopmjhijplpjhlplfkhba|Mymail-Crypt for Gmail]] ([[https://github.com/seancolyer/gmail-crypt/blob/master/LICENSE|License]]: GNU GPL v>=2) -- extension for Chrome/Chromium

Completeness: ?

Compatibility: ?

= PGPy

https://github.com/SecurityInnovation/PGPy/ based on https://pypi.python.org/pypi/cryptography which is based on ~OpenSSL

| License | BSD 3-Clause (and possibly other weak freedom-protecting licenses) |
| Programming Language/Environment | C and Python |
| Completeness | ? |
| Compatibility| ? |
| Used by  | ? |

= kbpgp

https://github.com/keybase/kbpgp

//Keybase's PGP for JS// claims:
//Public-key crypto and improvements to OpenPGP.js// 

| License | X11-style |
| Programming Language/Environment | Iced Coffescript compiling to Javascript |
| Completeness | ? |
| Compatibility| ? |
| Used by  | https://keybase.io/ (likely), though keybase also claims to use GnuPG and maintains a GnuPG-wapper module |


= NetPGP

http://www.netpgp.com/

| License | X11-style |
| Programming Language/Environment | C based on https://github.com/public/OpenPGP-SDK/ which based on OpenSSL |
| Completeness | [2] has: //NetPGP is useful but does not make up a full competitor to GnuPG.// |
| Compatibility| ? |
| Used by  | ? |

The latest versions offered on the website are from February 2014 and 2015 (last checked 2018-01-04).

= golang.org/x/crypto/openpgp

https://godoc.org/golang.org/x/crypto/openpgp

| License | Xorg-Style |
| Programming Language/Environment | Go |
| Completeness | ? |
| Compatibility| ? |
| Used by  | ? |

== GopenPGP
https://gopenpgp.org/

//a high-level OpenPGP wrapper library developed by ProtonMail, as well as a fork of the golang crypto library, which the wrapper library is built on.//

| License | Xorg-Style |
| Programming Language/Environment | Go |



= NeoPG 

https://neopg.io/

From the website: 
//NeoPG starts as an opiniated fork of GnuPG 2 to clean up the code and make it easier to develop. //

| License | GNU GPL v3 (and others like GnuPG) |
| Programming Language/Environment | C moving to C++ |
| Completeness | ? |
| Compatibility| (probably good because started as fork of GnuPG 2) |
| Used by  | ? |



= Sequoia PGP
* https://sequoia-pgp.org/
* https://gitlab.com/sequoia-pgp/sequoia

From the websites (2018-05-31):

//Sequoia is a cool new ~OpenPGP implementation. It consists of several crates, providing both a low-level and a high-level API for dealing with ~OpenPGP data.//

//Our work is made possible by the p≡p foundation.//

| License | ? (not speficied) |
| Programming Language/Environment | Rust (based on nettle and openssl? in C?) |
|  Completeness | ? |
| Compatibility| ? |
| Used by  | ? |





= Chromium Extension End-to-End

https://code.google.com/p/end-to-end/

| License | Apache 2.0 |
| Programming Language/Environment | Javascript, Chromium Extension |

Completeness: ? Claims to only create ECC certificates (which curve parameters?)

Compatibility: ?


* Google announced a Chromium extension that supports ~OpenPGP, see http://googleonlinesecurity.blogspot.de/2014/06/making-end-to-end-encryption-easier-to.html
* Heise newsarticle in DE: http://www.heise.de/newsticker/meldung/Google-experimentiert-mit-End-to-End-Verschluesselung-fuer-GMail-2215680.html

= Android Privacy Guard 
http://thialfihar.org/projects/apg/

| License | GPL 3+ |
| Programming Language/Environment | Java, Android SDK |

Completeness: ?

Compatibility: ?

Integrates with the K-9 Mailer.

Seems to be **unmaintained** (last release 2014-03, some known vulnerabilities unfixed since (status 2016-04)) with ~OpenKeychain
being the activeley maintained "fork", see 
[[https://www.openkeychain.org/faq/#what-is-the-relationship-between-apg-and-openkeychain|~OpenKeychain FAQ: relation to APG]]


= OpenPGP-Keychain

https://www.openkeychain.org/, started as [[https://github.com/open-keychain/open-keychain/blame/258cd4c8367d62515bf71f4a919b3cf67aa04e65/OpenKeychain/src/main/res/raw/help_faq.md#L111|a continuation of APG]].
Uses a repackaged Bouncy Castle: https://rtyley.github.io/spongycastle/

| License | GPL 3+ |
| Programming Language/Environment | Java, Android SDK |

Completeness: ?

Compatibility: ?

Integrates with the K-9 Mailer.


= Bouncy Castle
[[https://en.wikipedia.org/wiki/Bouncy_Castle_(cryptography)]]
(Homepage with ads: https://bouncycastle.org/)


| License | MIT |
| Programming Language/Environment | Java |

Completeness: ?

Compatibility: ?

= hOpenPGP
http://hackage.haskell.org/package/hOpenPGP

//native Haskell implementation of OpenPGP (RFC4880), plus Camellia (RFC5581) //

| License | MIT |
| Programming Language/Environment | Haskell |

= PGPro
https://pgpro.app

//iOS OpenPGP mail application

| License | GPL 3 |
| Programming Language | Swift / ObjectivePGP (non-Free dependency?) |

= FairEmail
https://email.faircode.eu/

//Android OpenPGP mail application

| License | GPL 3, with commercial option |
| Programming Language | Java, C++ |

= Discussion
 * https://news.ycombinator.com/item?id=7843297 Discussion about ~OpenPGP.js codequality and choice of reimplementation in End-to-End.
 * **[2]** https://lwn.net/Articles/742542/ (subscriber contents to become generally available ~10th of January, 2018) //Future directions for PGP//, January 3, 2018 by J. B. Crawford, lists ~NetPGP and ~NeoPGP.