DTLS, DTLS-SRTP
DTLS: Basically DTLS is to construct TLS over datagram (UDP, DCCP, etc.) DTLS is similar to TLS intentionally except that DTLS has to solve two problems: packet lost and reordering.…
OpenPGP vs S/MIME
S/MIME and OpenPGP similarity: both depends on public/private keys to encrypt/authenticate msg ( emails), difference: how to distribute the public keys. S/MIME is similar to TLS, need to depends on…
What is the difference between srtp and zrtp
SRTP sdp msg: v=0 o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5 s=SDP Seminar i=A Seminar on the session description protocol u=http://www.example.com/seminars/sdp.pdf e=j.doe@example.com (Jane Doe) c=IN IP4 161.44.17.12/127 t=2873397496 2873404696 m=video 51372…
systemctl cheatsheat
Systemd template and instance (@) from: https://wiki.archlinux.org/index.php/systemd Note: Some unit names contain an @ sign (e.g. name@string.service): this means that they are instances of a template unit, whose actual file…
SSH protocol
How SSH2 works: (1) When a TCP connection is made by a client, the server responds with the protocol versions it supports. If the client can match one of the…
TLS/SSL handshake
The combination of Diffie-Hellman and the use of ephemeral session keys are what enables “Forward Secrecy”: even if an attacker gains access to the server’s private key they are not…
Digital certificate vs digital signature
Digital Signature: how it works Digital certificate is one use cases of digital signature. To create the digital signature, the CA generates a message digest from the certificate, encrypts the…
how to update default session-manager for GDM3
I like to use gnome-flashback mode which is like old gnome2 desktop, but I keep on forgetting this how to set the default login session, so put notes here. sudo…
How C++11 lambda is implemented
Quota from a good article from http://www.cprogramming.com/c++11/c++11-lambda-closures.html It turns out that the way lambdas are implemented is by creating a small class; this class overloads the operator(), so that it…
Python @staticmethod, @classmethod
Found a good one to explain: How @staticmethod and @classmethod are different. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 class Kls(object): no_inst =…