Cryptography I course by Stanford

Online learning has gained much popularity these days. One of these courses is Cryptography I taken by Prof. Dan Boneh of Stanford University through Coursera Inc. I highly recommend this course for those who want to start learning this subject. Even if I have studied few topics of the subject back in college and done some self-study in it, I found the course to be somewhat different. The way of teaching is too good. The course material is a balance of both theoretical and practical aspects and it also highlights some of the open problems in cryptography. The learners need to watch few videos each week and need to answer questions at the end, which they get points for. There is a final test at the end of the course. After successfully taking the test, a certificate of accomplishment is generated within two to three days for the participant. I am waiting for its advanced course: Cryptography II. Readers are suggested to go through the references mentioned below for these courses.

References:

 Coursera

 Cryptography I

 Cryptography II 

SSH protocol overview

Secure Shell, as the name suggests, is a protocol for getting a shell which can be used to securely execute commands on a remote machine. It supports several other features too. It is a combination of three layers of protocols namely, Transport layer protocol, User authentication protocol and Connection protocol [See references below for RFC links]. 

Transport layer protocol provides confidential channel over insecure network. This layer provides server host authentication, key exchange, encryption, integrity protection. It derives session id that may be used by higher level protocols.

User authentication protocol provides a suite of mechanism that can be used to authenticate the client user to the server.

Connection protocol specifies a mechanism to multiplex multiple streams (channels) of data over the confidential and authenticated transport. It also specifies channels for accessing an interactive shell, for proxy-forwarding various external protocols over the secure transport (including arbitrary TCP/IP protocols) and for accessing secure subsystems on the server host. 

OpenSSH is a wonderful implementation of SSH available online [See below for references].

Few references:

 SSH Protocol Architecture

 Transport Layer Protocol

 User authentication Protocol

 Connection Protocol 

 Wiki-SSH

 OpenSSH
 Wiki-OpenSSH