When I shutdown Tails, various standard messages appear including the statement that if the system does not power-off, then it is likely that the memory wiping process has failed. More curiously, I notice that something along the following lines appears: "Warning, memory wipe is insecure (using 0x00)".
I can understand why overwriting memory with 0x00 might be considered insecure ... but if it is insecure, why do it? Why is Tails not overwriting the memory using random bytes?
Tails uses sdmem from the secure-delete package to overwrite RAM on shutdown, see https://tails.boum.org/contribute/design/memory_erasure/ for details.
According to that page, "memory is only overwritten once with zeros; this is the fastest available mode, and is enough to protect against every memory forensics attack we know of".
sdmem also supports a "secure" mode that uses 38 passes with different bit patterns, based on Peter Gutmann's paper "Secure Deletion of Data from Magnetic and Solid-State Memory", however it's not clear how applicable this research is to RAM and protection against cold boot attacks.
It is about Tails being in a kindergarten stage - it's a very good idea behind the scenes, but the implementation itself is too raw and unfinished nowdays. Give it a time! I myself was very disappointed about what it was a year ago; now it's still raw, but much better - don't be hasty! I'm starting to make my own Linux distro now, and I'm introducing some differences into the very good-debugged process of Debian distro making, and I can see how huge the challenges are - they just seems to be small and tiny at the start and from a side-view point, but inside there's a hell-ton of job to do. A difficult one, the one no one else has done before you, so you can't just Google it
