Use /dev/random to create a key

[sunwire]

Use /dev/random file to create a new key instead of rand() function. It provides much more cryptographically secure random output.

[JoelStienlet]

Thanks A LOT for seeing this blunder! The way it was coded was not secure at all, everybody should consider their tape entirely unencrypted.
How you can crack "encrypted" tapes:
rand() is a deterministic function. The only random part of the previous code was to read a random input from getchar().
But: getchar() will only take ~200 different values. So, summing (with the usual "+", the operation is not crypto at all !) lets say 20 characters, each taking a number between 0 and 200, you end up with a srand() seed between 0 and 4000. That's it, by simply testing ~4000 combinations you can crack the "encryption".

[marianrh]

Since this hasn't been merged in a few months now, I'd just like to leave my method of creating a random key here for other people stumbling over this issue:
xxd -l 32 -c 32 -p /dev/random

[ninthclowd]

Unfortunately I have no way to test this atm. Would someone else validate and do the pull request?

[fpiecka]

The change seems pretty good to me.

I've successfuly built the program and I've tested it on Linux both with and without /dev/random being available.