mvlad
The main distinctive features of LTTng is that it produces correlated kernel and user space traces, as well as doing so with the lowest overhead amongst other solutions. It produces trace files in the CTF format, an optimized file format for production and analyses of multi-gigabyte data. LTTng is the result of close to 10 years of active development by a community of passionate developers. It is currently available on all major desktop and embedded Linux distributions."
Further down you'll discover that your application(s) are linked with a library provided by the project.
Most of them rely on kprobes [1], or like ftrace on [2]. But there is also oprofile [3], and almighty perf [4], which rely on CPU extensions to implement tracing, (also implemented and by the HW manufacturer as well -- but in a OS-agnostic way).
[1] http://lxr.free-electrons.com/source/Documentation/kprobes.t...
[2] http://lxr.freeelectrons.com/source/Documentation/filesystem...
[3] http://oprofile.sourceforge.net/doc/internals/index.html
For people really interested in crypto there's obiously HAC [1].
For people interested in something that is updated each year: LNCS from DIMVA and RAID are quite good for understanding the problems or future problems and their solutions.
And of course phrack?
Let's not mix apples with oranges.
Privacy will always be a issue when you want an ``enriched experience'' from that app (although in some cases, privacy it is just being abused from other malign or commercial value).