SC4 is a secure communications system specifically designed for (relatively) easy auditability by way of a ruthless commitment to simplicity. SC4 provides the functional equivalent of PGP from the end-user's point of view, but implements it in two order of magnitude less code. The cryptographic core of SC4 is Daniel J. Bernstein's TweetNaCl library (<800 LOC). On top of this we have a variety of UI implementations ranging from 1000 to 5000 LOC. One of these has completed a formal audit to date.

OpenSSL software - a robust, commercial-grade, full-featured toolkit for general-purpose cryptography and secure communication.

This document attempts to give you the tools needed to answer questions and explain the mysteries of gpg and PGP so that you too can take advantage of this tool and stop making excuses.
Found on https://rgoulter.com/blog/posts/programming/2022-06-10-a-visual-explanation-of-gpg-subkeys.html
See also https://github.com/dmshaw/paperkey and https://github.com/jonathancross/jc-docs

Found on http://www.pfarrell.com/

Available for Linux, OS X and Windows. More details can be found on https://www.primx.eu/en/encryption-software/zed-en/
ALGORITHMS: AES (128 to 256 bits) and RSA (1024 to 4096 bits).
TECHNOLOGIES: PKCS#1, PKCS#5, PKCS#11, X509, Microsoft CSP, LDAP technologies, PKIx compatible.
 PKCS#1 RSA Cryptography Standard https://en.wikipedia.org/wiki/PKCS_1
 PKCS#5 Password-based Encryption Standard https://en.wikipedia.org/wiki/PBKDF2
 PKCS#11 Cryptographic Token Interface https://en.wikipedia.org/wiki/PKCS_11
 X509 https://en.wikipedia.org/wiki/X.509 (ITU) standard defining the format of public key certificates.
 Does CSP stand for https://en.wikipedia.org/wiki/Credential_service_provider , Cloud service provide https://mymatetech.net/what-is-microsoft-csp-ab5b80519e79 or something else?
 LDAP https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol
 Does PKIx stand for https://en.wikipedia.org/wiki/X.509#PKIX_Working_Group ?

SYSTEMS: Available for Windows 11 to Windows 7, Linux (various distributions) and Mac OS.
LANGUAGES: Available in 7 languages.
ZED! mobile app for iOS and Android.

This repository documents how to implement custom FIDO2 extensions. It contains supplementary material to our paper at ETAA 2021. We describe how to implement extensions on all parts of the FIDO2 stack: On the relying party (website), on the client (browser), and on the authenticator (hardware token).

Found via https://positive.security/blog/find-you and https://github.com/seemoo-lab/openhaystack

Critical review of some of the design choices made in the cryptographic tool 'age'.
There are other interesting articles, such as the three-part series
https://neilmadden.blog/2018/11/14/public-key-authenticated-encryption-and-why-you-want-it-part-i/
https://neilmadden.blog/2018/11/26/public-key-authenticated-encryption-and-why-you-want-it-part-ii/
https://neilmadden.blog/2018/12/14/public-key-authenticated-encryption-and-why-you-want-it-part-iii/
and
https://neilmadden.blog/2016/09/13/critical-thinking-for-software-engineers

Looks interesting. While not brand new (2017-11), it is more up-to-date than the HAC (5th printing 2001).

Need to encode, transmit, or store encrypted or signed data? saltpack is a streamlined, modern solution, designed with simplicity in mind. It is easy to implement & integrate. We've made few crypto decisions and instead leave almost all of the heavy lifting to the NaCl library.

saltpack is a binary message format, encoded using the MessagePack format. Messages are broken up into reasonable (1MB) chunks, over which regular NaCl operations are performed. We have taken pains to address many of the shortcomings of current message formats: (1) only authenticated data is output; (2) repudiable authentication is used wherever possible; (3) chunks cannot be reordered or combined with other transmissions; (4) the public keys of senders and recipients can be hidden; and (5) message truncation is detectable.

Implementations in Go and Python are available at https://saltpack.org/implementations  The format is used by https://keybase.io/

Found on https://www.metzdowd.com/pipermail/cryptography/2021-April/036859.html
"The really important thing is the theory paper, https://www.cs.ucdavis.edu/~rogaway/aez/rae.pdf, which is brilliant and anyone who wants to look at block cipher theory should read and understand it."