https://www.ietf.org/rfc/rfc3161
http://truetimestamp.org/
https://opentimestamps.org/
https://www.freetsa.org/index_en.php
https://ca.signfiles.com/tsa/
https://www.globalsign.com/en/timestamp-service?signature=sha2
http://tsp.iaik.tugraz.at/tsp/
http://time.certum.pl/
http://dss.nowina.lu/pki-factory/tsa/list
https://www.apple.com/certificateauthority/
http://oscp.cocbuilder.su/
https://safestamper.com/tsa
http://timestamp.globalsign.com/scripts/timstamp.dll
https://timestamp.geotrust.com/tsa
http://timestamp.comodoca.com/rfc3161
http://timestamp.wosign.com
http://tsa.startssl.com/rfc3161
http://time.certum.pl
http://timestamp.digicert.com
https://freetsa.org
http://dse200.ncipher.com/TSS/HttpTspServer
http://tsa.safecreative.org
http://zeitstempel.dfn.de
https://ca.signfiles.com/tsa/get.aspx
http://services.globaltrustfinder.com/adss/tsa
https://tsp.iaik.tugraz.at/tsp/TspRequest
http://timestamp.apple.com/ts01
http://timestamp.entrust.net/TSS/RFC3161sha2TS
https://gist.github.com/Manouchehri/fd754e402d98430243455713efada710
https://www.bigchaindb.com/
https://zkproof.org/
https://couchdb.apache.org/
https://pouchdb.com/external.html
https://holochain.org/
https://hazelcast.org/
https://www.cockroachlabs.com/
https://riak.com/
http://qrng.anu.edu.au/index.php
http://random.irb.hr/
https://qrng.physik.hu-berlin.de/
https://www.qutools.com/qurng/
https://www.qutools.com/qutag/qutag-qutau-applications/
- https://fedorahosted.org/freeotp/wiki
- https://openrepos.net/content/seiichiro0185/sailotp
- https://github.com/markmcavoy/androidtoken
- http://blogs.forgerock.org/petermajor/2014/02/one-time-passwords-hotp-and-totp/
- https://www.rcdevs.com/tokens/ --- comercial
- http://www.freeipa.org/page/Downloads
- https://github.com/w8rbt/oathgen
- http://www.nongnu.org/oath-toolkit/
- http://linotp.org/
- https://forgerock.org/openam/
- https://www.privacyidea.org/
- http://www.openauthentication.org/
- https://quickhash.com/
- https://github.com/ogay/hmac
- http://www.cryptopp.com/
- http://www.drdobbs.com/security/the-hmac-algorithm/184410908
- https://tools.ietf.org/html/rfc6234
- https://tools.ietf.org/html/rfc4868
- http://www.opensource.apple.com/source/ntp/ntp-70/lib/isc/hmacsha.c
- http://en.wikipedia.org/wiki/Hash-based_message_authentication_code
- http://rosettacode.org/wiki/RIPEMD-160
- https://tools.ietf.org/html/rfc6238
- https://tools.ietf.org/html/rfc4226
- https://tools.ietf.org/html/rfc5741
- https://guide.duosecurity.com/third-party-accounts
- https://help.github.com/articles/configuring-two-factor-authentication-via-a-totp-mobile-app/
- http://jacob.jkrall.net/totp/
- http://security.stackexchange.com/questions/37203/what-are-the-security-implications-of-using-totp-for-single-factor-authenticatio
- ftp://ftp.deas.harvard.edu/techreports/tr-22-06.pdf
- http://cs.brown.edu/~foteini/papers/MathTRE.pdf
- http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange
- http://people.csail.mit.edu/rivest/RivestShamirWagner-timelock.pdf
- http://people.csail.mit.edu/rivest/lcs35-puzzle-description.txt --- cod java
- http://people.seas.harvard.edu/~salil/research/timelock.pdf
- https://github.com/google/google-authenticator/ --- implementarea goagăl, că tot e pe sticlă tov. Vanghele, cu versiuni pentru mobile
- http://rosettacode.org/wiki/Time-based_One-time_Password_Algorithm --- exemple de implementari in mai multe limbaje de programare
- http://blogs.technet.com/b/cloudpfe/archive/2014/10/26/using-time-based-one-time-passwords-for-multi-factor-authentication-in-ad-fs-3-0.aspx
- https://blog.nraboy.com/2014/10/generate-time-based-one-time-passwords-javascript/ --- JS
- https://gitorious.org/hotp-js --- JS HMAC
- http://motp.sourceforge.net/ --- J2ME, Android, iOS si multe referinte
- http://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-04