By User:Salimfadhley (Own work) [GFDL ( or CC-BY-SA-3.0 (], via Wikimedia Commons

4-way TCP handshake and firewalls

Jarek Siembida wrote “This is one of those pieces that you keep in your head for ages but never get around to write up. Tcpdumping I was doing of late brought it back so here it is. We all know the 3-way handshake in TCP: SYN + SYN/ACK + ACK and voila! But this is not the end…”

By Ixocactus (Own work) [CC BY-SA 4.0 (], via Wikimedia Commons

ECMAScript 6

Jarek Siembida wrote “Recent projects got me dealing with JavaScript and this got me thinking about the language. You know, The Bad Parts. The damage has been done and there is no simple way to backpedal out of it. But hey, there is ECMAScript 6 to our rescue, is there not? Its final shape and form is known…”

By Rept0n1x (Own work) [GFDL ( or CC-BY-SA-3.0-2.5-2.0-1.0 (], via Wikimedia Commons

Optimizing Salsa20 in BouncyCastle

Jarek Siembida wrote “A while ago I started dabbling in cryptography a bit, and inevitably, I ended up toying with performance of the related algorithms and code. In this post I’d like to share my approach to optimizing BouncyCastle’s implementation of Salsa20. A few observations regarding Salsa20 (and presumably other modern ciphers) in the context of performance: Salsa20…”

By StromBer (Own work) [CC BY 3.0 (], via Wikimedia Commons

Optimizing loops in C for higher numerical throughput and for fun

Jarek Siembida wrote “We had here, in LShift, this typical C-vs-Fortran discussion which prompted me to follow up on it. In this holy war I stand by C and believe that a lot of opinions supporting the alleged superiority of Fortran in numerical throughput come from poor understanding of what actually can be done on the C side.…”

CPU cache collisions in the context of performance

Jarek Siembida wrote “This article discusses some potential performance issues caused by CPU cache collisions. In normal scenarios cache collisions don’t pose a problem, it usually is only in specific, high speed applications that they may incur noticeable performance penalties, and as such, things described here should be considered “the last mile effort”. As an example, I will…”