Redphone, Truecrypt, PGP and OTR
https://www.google.com/about/appsecurity/tools/
https://developer.mozilla.org/en-US/docs/Tools
pngout http://advsys.net/ken/utils.htm
https://securityheaders.com/
https://code.google.com/p/domsnitch/
http://www.cryptix.org/
http://www.gnu.org/software/gnu-crypto/
https://code.google.com/p/cryptsetup/
https://github.com/bitwiseshiftleft/sjcl
http://pajhome.org.uk/crypt/index.html
http://codecrawler.sourceforge.net/
http://h3xstream.github.io/find-sec-bugs/
https://w3dt.net/ ✩✩✩
https://www.soldierx.com/tools ✩✩✩✩✩
http://openpgpjs.org/
https://github.com/ziyan/ssh-otp
https://cheapsslsecurity.com/ssltools/
https://www.securityinnovation.com/security-lab/tools/
Related: Study_Security_EncryptionAlgorithm